Semiconductor element, organic transistor, light-emitting device, and electronic device

ABSTRACT

It is an object of the present invention to provide an organic transistor having a low drive voltage. It is also another object of the present invention to provide an organic transistor, in which light emission can be obtained, which can be manufactured simply and easily. According to an organic light-emitting transistor, a composite layer containing an organic compound having a hole-transporting property and a metal oxide is used as part of the electrode that injects holes among source and drain electrodes, and a composite layer containing an organic compound having an electron-transporting property and an alkaline metal or an alkaline earth metal is used as part of the electrode that injects electrons, where either composite layer has a structure of being in contact with an organic semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/498,512, filed Jul. 7, 2009, now allowed, which is a divisional ofU.S. application Ser. No. 11/379,014, filed Apr. 17, 2006, now U.S. Pat.No. 7,560,735, which claims the benefit of a foreign priorityapplication filed in Japan as Serial No. 2005-125807 on Apr. 22, 2005,all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor element that can beused as a switching element or an amplifier element (for example, anorganic transistor). In addition, the present invention relates to alight-emitting device with the use thereof.

2. Description of the Related Art

It has been promoted to develop a light-emitting element where electronsare injected from one electrode and holes are injected from the otherelectrode into a stacked body containing an organic compound sandwichedbetween the pair of electrodes to recombine the electrons and holes inthe stacked body so that a light-emitting material in the stacked bodyis excited and thus light emission can be obtained.

Being a self-light-emitting type, the light-emitting element is superiorin visibility with low dependence on a viewing angle and a thin shapeand weight saving can be realized easily. Therefore, attention isfocused on the use of a flat panel display of the next generation. Inaddition, it is also possible to manufacture an element in a flexiblefilm such as plastic, the usage of which is expected as a mobiledisplay.

A light-emitting device using this light-emitting element can be roughlydivided into two types, that is, a passive matrix type and an activematrix type. In the active matrix light-emitting device, a transistor iselectrically connected in each pixel to control light emission of alight-emitting element.

Thus far, an inorganic semiconductor material typified by silicon hasbeen used for a transistor of the active matrix light-emitting device.However, it is necessary to process at high temperature in order to formthe inorganic semiconductor material typified by silicon as asemiconductor layer; therefore, it is difficult to use a flexiblematerial such as plastic or a film for a substrate.

On the other hand, a transistor in which an organic semiconductormaterial is used as a semiconductor layer can be formed even atcomparatively low temperature; therefore, it is possible to manufacturein principle a transistor not only over a glass substrate but also overa substrate having low heat resistance such as plastic.

In such a manner, as an example of a field effect transistor in whichthe organic semiconductor material is used as a semiconductor layer(hereinafter, referred to as an “organic transistor”), a transistor inwhich silicon dioxide (SiO₂) is used as a gate insulating layer andpentacene is used as a semiconductor layer (see the following Reference1: Y. Y. Lin, D. J. Gundlach, S. F. Nelson, T. N. Jackson, IEEE ElectronDevice Letters, Vol. 18, pp. 606-608 (1997)) can be given. In thisreport, it is reported that field effect mobility is 1 cm²/Vs andtransistor performance comparable to amorphous silicon can be obtainedeven when the organic semiconductor material is used as a semiconductorlayer.

An active matrix light-emitting device in which a light-emitting elementis driven using this organic transistor is also proposed. Further, thereare several reports regarding an organic transistor in which holes areinjected from a source electrode and electrons are injected from a drainelectrode into an organic semiconductor layer thereof to recombine theholes and electrons in the semiconductor layer and thus light emissionis obtained from the organic semiconductor layer itself (hereinafter,referred to as an organic light-emitting transistor) (see Reference 2:M. Ahles, A. Hepp, R. Schmechel, F. v. Seggern, APPLIED PHYSICS LETTERS,Vol. 84, No. 3, pp. 428-430 (2004) and Reference 3: T. Sakanoue, E.Fujiwara, R. Yamada, H. Tada, Chemistry Letters, Vol. 34, No. 4, pp.494-495 (2005), for example).

Since these organic light-emitting transistors are elements having bothfunctions of a transistor and a light-emitting element, it is consideredthat the organic light-emitting transistors are advantageous in anaperture ratio compared with a case of manufacturing a transistor, whichdrives a light-emitting element, separately from a light-emittingelement. In addition, since a manufacturing element is reduced comparedwith the case of manufacturing both a transistor and a light-emittingelement, it is considered that the organic light-emitting transistorsare advantageous also in a yield or a manufacturing cost of a product.

In the meantime, in the organic light-emitting transistor, holes andelectrons have to be injected into a semiconductor layer from a sourceelectrode and a drain electrode in order to obtain light emission;however, there are such problems that light emission does not occurwell, a transistor characteristic such as carrier mobility is decreased,or a drive voltage is increased when there is an energy barrier in theinterface.

The energy barrier in injecting holes and electrons into a semiconductorlayer depends on a relation between a material used for electrodes andan organic semiconductor material and largely influences a work functionof the material used for electrodes. Therefore, an electrode materialthat allows holes and electrons to be injected into a semiconductorlayer efficiently, and that can reduce a drive voltage has an extremelynarrow option.

Further, in forming a metal electrode, there is a case where the workfunction may be changed due to etching in forming the electrode or acase where the lower layer may be deteriorated; thus, it is not easy toobtain an organic light-emitting transistor having a low drive voltagewhich can be manufactured simply and easily.

SUMMARY OF THE INVENTION

Thus, it is an object of the present invention to provide asemiconductor element having a low drive voltage. In addition, it isanother object of the present invention to provide a semiconductorelement, in which light emission can be obtained and the light emissioncan be controlled by itself, which can be manufactured simply andeasily.

In addition, it is another object of the present invention to provide anorganic transistor having a low drive voltage. It is also another objectof the present invention to provide an organic transistor, in whichlight emission can be obtained and the light emission can be controlledby changing voltage of a gate electrode, which can be manufacturedsimply and easily.

Moreover, it is another object of the present invention to provide alight-emitting device having a high aperture ratio and yield. Further,it is another object of the present invention to provide alight-emitting device that can be manufactured more simply and easily.Furthermore, it is the other object of the present invention to providea light-emitting device having a low drive voltage and powerconsumption.

The present inventors reached the conclusion on the basis of their keenexamination that the above problems can be solved by an organiclight-emitting transistor in which a composite layer containing anorganic compound having a hole-transporting property and a metal oxideis used as part of an electrode that injects holes among source anddrain electrodes and a composite layer containing an organic compoundhaving an electron-transporting property and an alkaline metal or analkaline earth metal is used as part of the electrode that injectselectrons, where either composite layer has a structure of being incontact with an organic semiconductor layer.

According to one feature of the present invention, a semiconductorelement includes a first electrode; a semiconductor layer containing anorganic compound; an insulating film which electrically insulates thefirst electrode and the semiconductor layer; a second electrode whichinjects electrons into the semiconductor layer; and a third electrodewhich injects holes into the semiconductor layer, wherein the thirdelectrode has at least partially a layer made of a first compositematerial containing an organic compound having a hole-transportingproperty and a metal oxide, wherein the second electrode has at leastpartially a layer made of a second composite material containing anorganic compound having an electron-transporting property and alkalinemetal or alkaline earth metal, and wherein the layer made of the firstcomposite material and the layer made of the second composite materialare each in contact with the semiconductor layer.

In the above structure of a semiconductor element according to thepresent invention, the second electrode is formed of two layers of thelayer made of the first composite material and a conductive layer. Whenthe conductive layer is not in contact with the semiconductor layer, thelength of a channel length direction of the conductive layer may beshorter than the length of a channel length direction of the layer madeof the first composite material. In addition, the conductive layer maybe covered with the layer made of the first composite material. When theconductive layer is in contact with the semiconductor layer, theconductive layer may be covered with the layer made of the firstcomposite material.

In the above structure of a semiconductor element according to thepresent invention, the third electrode is formed of two layers of thelayer made of the second composite material and a conductive layer. Whenthe conductive layer is not in contact with the semiconductor layer, thelength of a channel length direction of the conductive layer may beshorter than the length of a channel length direction of the layer madeof the second composite material. In addition, the conductive layer maybe covered with the layer made of the second composite material. Whenthe conductive layer is in contact with the semiconductor layer, theconductive layer may be covered with the layer made of the secondcomposite material.

In the above structure of a semiconductor element according to thepresent invention, the second electrode further has the layer made ofthe second composite material, and the layer made of the first compositematerial and the layer made of the second composite material are atleast partially in contact with each other. In addition, the secondelectrode is formed of three layers of the layer made of the firstcomposite material, the layer made of the second composite material, anda conductive layer.

In the above structure of a semiconductor element according to thepresent invention, the third electrode further has the layer made of thefirst composite material, and the layer made of the first compositematerial and the layer made of the second composite material are atleast partially in contact with each other. In addition, the thirdelectrode is formed of three layers of the layer made of the firstcomposite material, the layer made of the second composite material, anda conductive layer.

According to one feature of the present invention, an organic transistorincludes a gate electrode; a semiconductor layer containing an organiccompound; an insulating film which electrically insulates the gateelectrode and the semiconductor layer; a source electrode; and a drainelectrode, wherein the source electrode has at least partially a layermade of a first composite material containing an organic compound havinga hole-transporting property and a metal oxide, wherein the drainelectrode has at least partially a layer made of a second compositematerial containing an organic compound having an electron-transportingproperty and alkaline metal or alkaline earth metal, and wherein thelayer made of the first composite material and the layer made of thesecond composite material are each in contact with the semiconductorlayer.

In the above structure of an organic transistor according to the presentinvention, the source electrode is formed of two layers of the layermade of the first composite material and a conductive layer. When theconductive layer is not in contact with the semiconductor layer, thelength of a channel length direction of the conductive layer may beshorter than the length of a channel length direction of the layer madeof the first composite material. In addition, the conductive layer maybe covered with the layer made of the first composite material. When theconductive layer is in contact with the semiconductor layer, theconductive layer may be covered with the layer made of the firstcomposite material.

In the above structure of an organic transistor according to the presentinvention, the drain electrode is formed of two layers of the layer madeof the second composite material and a conductive layer. When theconductive layer is not in contact with the semiconductor layer, thelength of a channel length direction of the conductive layer may beshorter than the length of a channel length direction of the layer madeof the second composite material. In addition, the conductive layer maybe covered with the layer made of the second composite material. Whenthe conductive layer is in contact with the semiconductor layer, theconductive layer may be covered with the layer made of the secondcomposite material.

In the above structure of an organic transistor according to the presentinvention, the source electrode further has the layer made of the secondcomposite material, and the layer made of the first composite materialand the layer made of the second composite material are at leastpartially in contact with each other. In addition, the source electrodeis formed of three layers of the layer made of the first compositematerial, the layer made of the second composite material, and aconductive layer.

In the above structure of an organic transistor according to the presentinvention, the drain electrode further has the layer made of the firstcomposite material, and the layer made of the first composite materialand the layer made of the second composite material are at leastpartially in contact with each other. In addition, the drain electrodeis formed of three layers of the layer made of the first compositematerial, the layer made of the second composite material, and aconductive layer.

According to another feature of the present invention, an organictransistor includes a gate electrode; a semiconductor layer containingan organic compound; an insulating film which electrically insulates thegate electrode and the semiconductor layer; a source electrode; and adrain electrode, wherein the source electrode has at least partially alayer made of a second composite material containing an organic compoundhaving an electron-transporting property and alkaline metal or alkalineearth metal, wherein the drain electrode has at least partially a layermade of a first composite material containing an organic compound havinga hole-transporting property and a metal oxide, and wherein the layermade of the first composite material and the layer made of the secondcomposite material are each in contact with the semiconductor layer.

In the above structure of an organic transistor according to the presentinvention, the source electrode is formed of two layers of the layermade of the second composite material and a conductive layer. When theconductive layer is not in contact with the semiconductor layer, thelength of a channel length direction of the conductive layer may beshorter than the length of a channel length direction of the layer madeof the second composite material. In addition, the conductive layer maybe covered with the layer made of the second composite material. Whenthe conductive layer is in contact with the semiconductor layer, theconductive layer may be covered with the layer made of the secondcomposite material.

In the above structure of an organic transistor according to the presentinvention, the drain electrode is formed of two layers of the layer madeof the first composite material and a conductive layer. When theconductive layer is not in contact with the semiconductor layer, thelength of a channel length direction of the conductive layer may beshorter than the length of a channel length direction of the layer madeof the first composite material. In addition, the conductive layer maybe covered with the layer made of the first composite material. When theconductive layer is in contact with the semiconductor layer, theconductive layer may be covered with the layer made of the firstcomposite material.

In the above structure of an organic transistor according to the presentinvention, the source electrode further has the layer made of the firstcomposite material, and the layer made of the first composite materialand the layer made of the second composite material are at leastpartially in contact with each other. In addition, the source electrodeis formed of three layers of the layer made of the first compositematerial, the layer made of the second composite material, and aconductive layer.

In the above structure of an organic transistor according to the presentinvention, the drain electrode further has the layer made of the secondcomposite material, and the layer made of the first composite materialand the layer made of the second composite material are at leastpartially in contact with each other. In addition, the drain electrodeis formed of three layers of the layer made of the first compositematerial, the layer made of the second composite material, and aconductive layer.

In the above structure of an organic transistor according to the presentinvention, the semiconductor layer emits light when voltage is appliedbetween the source electrode and the drain electrode, and emissionluminance is changed by changing voltage applied to the gate electrode.

A semiconductor element according to the present invention has a lowdrive voltage. In addition, the semiconductor element according to thepresent invention, in which light emission can be obtained and the lightemission can be controlled by the semiconductor element itself, can bemanufactured simply and easily.

An organic transistor according to the present invention has a low drivevoltage. In addition, the organic transistor according to the presentinvention, in which light emission can be obtained and the lightemission can be controlled by changing voltage of a gate electrode, canbe manufactured simply and easily.

Moreover, a light-emitting device according to the present invention hasa high aperture ratio and high yields. Further, the light-emittingdevice according to the present invention can be manufactured simply andeasily. Furthermore, the light-emitting device has a low drive voltage.

These and other objects, features and advantages of the presentinvention will become more apparent upon reading of the followingdetailed description along with the accompanied drawings.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 2A to 2C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 3A to 3D are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIG. 4 is a schematic top view of an organic light-emitting transistoraccording to the present invention;

FIGS. 5A to 5C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 6A to 6C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 7A to 7D are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 8A to 8D are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 9A to 9C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 10A to 10C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 11A to 11C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 12A to 12C are each a schematic cross-sectional view of an organiclight-emitting transistor according to the present invention;

FIGS. 13A to 13E are views each showing a manufacturing method of anorganic light-emitting transistor according to the present invention;

FIGS. 14A and 14B are each schematic cross-sectional and top views of alight-emitting device according to the present invention;

FIGS. 15A to 15C are views each showing an electronic device accordingto the present invention; and

FIG. 16 is a view showing an electronic device according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment Modes of the present invention will be explained below withreference to the accompanying drawings. However, it is to be easilyunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless such changes andmodifications depart from the scope of the invention, they should beconstrued as being included therein.

Embodiment Mode 1

A semiconductor element which is an embodiment mode of the presentinvention will be explained by giving drawings illustrated in FIGS. 1Ato 1C, FIGS. 2A to 2C, FIGS. 3A to 3D, FIG. 4, FIGS. 5A to 5C, FIGS. 6Ato 6C, FIGS. 7A to 7D, and FIGS. 8A to 8D as examples.

A semiconductor element according to the present invention illustratedin FIG. 1A includes a first electrode 100, an insulating film 101, asemiconductor layer 102, a second electrode 107, and a third electrode108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film which is not shown, and theinsulating film 101 electrically insulates the semiconductor layer 102and the first electrode 100. In addition, the second electrode 107 isformed of two layers of a conductive layer 105 a and a layer 103 made ofa second composite material and the third electrode 108 is formed of twolayers of a conductive layer 105 b and a layer 104 made of a firstcomposite material, respectively. The layer 103 made of the secondcomposite material in the second electrode 107 and the layer 104 made ofthe first composite material in the third electrode 108 are provided tobe in contact with the semiconductor layer 102. The conductive layer 105a and the conductive layer 105 b may not be in contact with thesemiconductor layer 102.

Although not shown, among insulators where the first electrode 100 canbe formed, as for a substrate, an insulating substrate such as a glasssubstrate; a quartz substrate; or a crystalline glass, a ceramicsubstrate, a stainless steel substrate, a metal substrate (such astantalum, tungsten, or molybdenum), a semiconductor substrate, a plasticsubstrate (polyimide, acrylic, polyethylene terephthalate,polycarbonate, polyarylate, or polyethersulfone), or the like can beused. In addition, an insulating film formed from an inorganicinsulating material such as silicon oxide, silicon nitride, siliconoxide containing nitrogen, and silicon nitride containing oxygen, anorganic insulating material such as acrylic or polyimide, or a materialcomposed of a skeleton structure formed by the bond of silicon andoxygen, in which an organic group at least containing hydrogen (such asan alkyl group or an aryl group), a fluoro group, or an organic group atleast containing hydrogen and a fluoro group are included as asubstituent, that is, a siloxane-based material may be formed over sucha substrate. These insulating films may be formed by any of knownmethods such as a CVD method, a sputtering method, a vapor depositionmethod, and a wet method.

The materials of the first electrode 100, the conductive layer 105 a,and the conductive layer 105 b are not particularly limited, and thefollowing materials can be given as examples: a metal such as platinum,gold, aluminum, chromium, nickel, cobalt, copper, titanium, magnesium,calcium, barium, natrium, or tungsten and an alloy containing thesemetals, a conductive high molecular compound such as polyaniline,polypyrrole, polythiophene, polyacetylene, or polydiacetylene, aninorganic semiconductor such as silicon, doped silicon, germanium, orgallium arsenic, and further a material in which acid (including Lewisacid), a halogen atom, a metal atom of an alkaline metal, an alkalineearth metal, or the like is doped. As for a conductive material used forsource and drain electrodes, metal is generally used in many cases.These first electrode 100, conductive layer 105 a, and conductive layer105 b may be formed by any of known methods such as a CVD method, asputtering method, a vapor deposition method, and a wet method.

The material of the insulating film 101 is also not particularlylimited, and the insulating film 101 may be formed of an insulating filmformed from an inorganic insulating material such as silicon oxide,silicon nitride, silicon oxide containing nitrogen, and silicon nitridecontaining oxygen, an organic insulating material such as acrylic orpolyimide, or a material composed of a skeleton structure formed by thebond of silicon and oxygen, in which an organic group at leastcontaining hydrogen (such as an alkyl group or aromatic hydrocarbon), afluoro group, or an organic group at least containing hydrogen and afluoro group, that is, a siloxane-based material.

Any one of a low molecular compound, a middle molecular compound, or ahigh molecular compound can be used as the material of the semiconductorlayer 102, and a kind thereof is not particularly limited. As thematerial, a polycyclic aromatic compound, a conjugated double bondsystem compound, a macrocycle compound, a metal phthalocyanine complex,a charge-transfer type complex, condensed ring tetracarboxylic aciddiimides, oligothiophenes, fullerenes, a carbon nanotube, and the likecan be given as examples. For example, polypyrrole, polythiophene,poly(3-alkylthiophene), polythienylenevinylene,poly(p-phenylenevinylene), polyaniline, polyazulene, poly pyrene, polycarbazole, polyselenophene, polyfuran, poly(p-phenylene), polyindole,polypyridadine, anthracene, tetracene, pentacene, hexacene, heptacene,pyrene, chrysene, perylene, coronene, terylene, ovalene, quoterylene,triphenodioxazine, triphenodithiazine, hexacene-6,15-quinone, polyvinylcarbazole, polyphenylene sulfide, polyvinylene sulphide, polyvinylpyridine, naphthalene tetracarboxylic acid diimide, anthracenetetracarboxylic acid diimide, C₆₀, C₇₀, C₇₆, C₇₈, C₈₄, and a derivativethereof can be used. In addition, as specific examples thereof, thereare pentacene, sexithiophene (6T), copper phthalocyanine,bis-(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiol), and rubrene which aregenerally considered as a p-type semiconductor, and7,7,8,8-tetracyanoquinodimethane (abbreviation: TCNQ),3,4,9,10-perylenetetracarboxylic dianhydride (abbreviation: PTCDA),1,4,5,8,-naphthalentetracarboxylic dianhydride (abbreviation: NTCDA),N,N′-dioctyl-3,4,9,10-perylenetracarboxylic diimide (abbreviation:PTCDI-C8H), copper hexadecafluoro phthalocyanine (abbreviation: F₁₆CuPc),3′,4′-dibutyl-5,5″-bis(dicyanomethylene)-5,5″-dihydro-2,2′:5′,2″-terthiophene)(an abbreviation: DCMT), and the like which are generally considered asan n-type semiconductor. Note that, in an organic semiconductor,characteristics of a p-type and an n-type are not peculiar to thesubstance but depends on relation with an electrode for injecting acarrier or intensity of an electric field at the time of injection.Although there is a tendency that the substance is likely to becomeeither an n-type or a p-type, there is a possibility of being a p-type,n-type, or a bipolar type. According to the present invention, at leastpart of the layer 103 made of the second composite material, the layer104 made of the first composite material in the third electrode 108, andthe like are provided to be in contact with the semiconductor layer 102.Accordingly, injection barriers of holes and electrons are decreased andit becomes possible to inject holes and electrons easily withoutapplying a great amount of electric fields. Therefore, it becomespossible to inject both carriers of a hole and an electron even with amaterial which generally has been said a p-type or an n-type; thus,light emission can be obtained as a result of recombination. In such amanner, as for the material of the semiconductor layer 102 according tothe present invention, it is possible to decrease increase of a drivevoltage or the like even with the material which generally has been saida p-type or an n-type. Note that a drive voltage can be reduced furtherby using a material having a high bipolar property, which is aninfinitely preferable structure.

Besides, it is possible to use the following materials as a compoundthat can be used as the material of the semiconductor layer 102 in asemiconductor element according to the present invention:4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD),4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl(abbreviation: DNTPD), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), phthalocyanine (abbreviation: H₂ Pc), vanadylphthalocyanine (abbreviation: VOPc), tris(8-quinolinolato)aluminum(abbreviation: Alq₃), 9,10-bis(2-naphthyl)anthracene (abbreviation:DNA), bis(2-methyl-8-quinolinolato)-4-phenylphenolato)aluminum(abbreviation: BAlq), or the like.

In addition, a material having a transporting property to holes orelectrons, or the both as a host material is, for example, as ahole-transporting material,4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD),4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl(abbreviation: DNTPD), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), phthalocyanine (abbreviation: H₂ Pc), copperphthalocyanine (CuPc), or vanadyl phthalocyanine (abbreviation: VOPc),as an electron-transporting material, a metal complex such astris(8-quinolinolato)aluminum (abbreviation: Alq₃);tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃);bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂);bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq); bis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp₂);bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂); orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BOX)₂), anoxadiazole derivative such as2-(4-biphenylyl)-5-(4-tert-buthylphenyl)-1,3,4-oxadiazole (abbreviation:PBD) or 1,3-bis[5-(p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7), a triazole derivative such as3-(4-biphenylyl)-4-phenyl-5-(4-tert-buthylphenyl)-1,2,4-triazole(abbreviation: TAZ) or3-(4-biphenylyl)-4-(4-ethylpheyl)-5-(4-tert-buthylphenyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproin (abbreviation: BCP),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), or 4,4-bis(5-methylbenzoxazol-2-yl)stilbene(abbreviation: BzOs), and as a material having a bipolar property, ananthracene derivative such as poly(2,5-thienylenevinylene)(abbreviation: PTV); poly(3-hexylthiophene-2,5-diyl) (abbreviation:P3HT); poly(9,9′-dioctyl-fluorene-co-bithiophene) (abbreviation: F8T2);or 9,10-di(2-naphthyl)-2-tert-butylanthracene (abbreviation: t-BuDNA), acarbazole derivative such as 4,4′-bis(N-carbazolyl)biphenyl(abbreviation: CBP), or the like. As for the material having atransporting property to holes or electrons, or the both as a hostmaterial, a host-guest type mixture material where a material thatserves as a light-emission center as a guest material is dispersed maybe used. The material that serves as a light-emission center as a guestmaterial may also be, for example, 9,10-di(2-naphthyl)anthracene(abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene(abbreviation: t-BuDNA), 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbreviation: DPVBi), coumarin 30, coumarin 6, coumarin 545, coumarin545T, perylene, rubrene, periflanthen,2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP),9,10-diphenylanthracene (abbreviation: DPA), 5,12-diphenyltetracene,4-dicyanomethylene)-2-methyl-6-[p-(dimethylamino)styryl]-4H-pyran(abbreviation: DCM1),4-(dicyanomethylene)-2-methyl-6-[2-(julolidin-9-yl)ethenyl]-4H-pyran(abbreviation: DCM2),4-(dicyanomethylene)-2,6-bis[p-(dimethylamino)styryl]-4H-pyran(abbreviation: BisDCM),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)](picolinate)iridium(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}(picolinate)iridium(abbreviation: Ir(CF₃ ppy)₂ (pic)),tris(2-phenylpyridinato-N,C^(2′))iridium (abbreviation: Ir(ppy)₃),(acetylacetonato)bis(2-phenylpyridinato-N,C^(2′))iridium (abbreviation:Ir(ppy)₂ (acac)),(acetylacetonato)bis[2-(2′-thienyl)pyridinato-N,C^(3′)]iridium(abbreviation: Ir(thp)₂ (acac)),(acetylacetonato)bis(2-phenylquinolinato-N,C^(2′)) iridium(abbreviation: Ir(pq)₂ (acac)), or(acetylacetonato)bis[2-(2′-benzothienyl)pyridinato-N,C^(3′)]iridium(abbreviation: Ir(btp)₂ (acac)). There is no limitation on theconcentration of the guest material in the host material but theconcentration is preferably approximately 5 to 8 wt. %.

The semiconductor layer 102 made of these materials may be formed by anyof methods such as a CVD method, a sputtering method, a vapor depositionmethod, and a wet method.

The second composite material that forms the layer 103 made of thesecond composite material is a material composed of an inorganiccompound and an organic compound having an electron-transportingproperty. As the inorganic compound, an alkaline metal and an alkalineearth metal, or oxide and nitride containing the metals are desirableand, specifically, lithium, natrium, potassium, cesium, magnesium,calcium, strontium, barium, lithium oxide, magnesium nitride, or calciumnitride is preferably used. In addition, as the organic compound havingan electron-transporting property, perylenetetracarboxylic anhydride anda derivative thereof, a perylenetetracarboxy diimide derivative,naphthalentetracarboxylic anhydride and a derivative thereof, anaphthalentetracarboxydiimide derivative, a metal phthalocyaninederivative, or fullerenes can be used. Additionally, a material made ofa metal complex or the like having a quinoline skeleton or abenzoquinoline skeleton such as tris(8-quinolinolato)aluminum(abbreviation: Alq₃), tris(4-methyl-8-quinolinolato)aluminum(abbreviation: Almq₃), bis(10-hydroxybenzo[h]-quinolinato)beryllium(abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq), or the like can be used. Besides, a material such as a metalcomplex having an oxazole-based ligand or a thiazole-based ligand suchas bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂) orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)₂) canalso be used. Further, other than the metal complex,2-(4-biphenylyl)-5-(4-tert-buthylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-buthylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-buthylphenyl)-4-(4-ethylpheyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproin (abbreviation: BCP), or the like can be used. The layer 103made of the second composite material can be manufactured by an alkalinemetal and an alkaline earth metal, or a co-evaporation method with oxideor nitride containing the metals and the organic compound having anelectron-transporting property. However, the layer 103 made of thesecond composite material may also be formed by any of a wet method andother known methods.

The first composite material that forms the layer 104 made of the firstcomposite material is a material composed of an inorganic compound andan organic compound having a hole-transporting property. As theinorganic compound, oxide or nitride of a transition metal are desirableand, specifically, zirconium oxide, hafnium oxide, vanadium oxide,niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, titanium oxide, manganese oxide, or rhenium oxide ispreferably used. In addition, as the organic compound having ahole-transporting property, an organic material having an arylaminogroup such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB); 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl(abbreviation: TPD); 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA);4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA);4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl(abbreviation: DNTPD); 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB); or 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), phthalocyanine (abbreviation: H₂ Pc), copperphthalocyanine (CuPc), vanadyl phthalocyanine (abbreviation: VOPc), orthe like can also be used.

In addition, such an organic material that will be represented by thefollowing general formula (1) can also be preferably used. As thespecific examples,3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2), and the like can be given. The first compositematerial using an organic compound having this structure is superior inthermal stability and reliability.

In the formula, each of R¹ and R³ may be the same or different, whichrepresents any of hydrogen; an alkyl group having 1 to 6 carbon atoms;an aryl group having 6 to 25 carbon atoms; a heteroaryl group having 5to 9 carbon atoms; an arylalkyl group; and an acyl group having 1 to 7carbon atoms, Ar¹ represents any of an aryl group having 6 to 25 carbonatoms and a heteroaryl group having 5 to 9 carbon atoms, R² representsany of hydrogen; an alkyl group having 1 to 6 carbon atoms; and an arylgroup having 6 to 12 carbon atoms, and R⁴ represents any of hydrogen; analkyl group having 1 to 6 carbon atoms; an aryl group having 6 to 12carbon atoms; and a substituent that will be represented by a generalformula (2). In the substituent represented by the general formula (2),R⁵ represents any of hydrogen; an alkyl group having 1 to 6 carbonatoms; an aryl group having 6 to 25 carbon atoms; a heteroaryl grouphaving 5 to 9 carbon atoms; an arylalkyl group; and an acyl group having1 to 7 carbon atoms, Ar² represents any of an aryl group having 6 to 25carbon atoms and a heteroaryl group having 5 to 9 carbon atoms, and R⁶represents any of hydrogen; an alkyl group having 1 to 6 carbon atoms;and an aryl group having 6 to 12 carbon atoms.

In addition, such an organic material that will be represented by any ofthe following general formulas (3) to (6) can also be preferably used.As the specific examples of such an organic compound that will berepresented by any of the following general formulas (3) to (6),N-(2-naphthyl)carbazole (abbreviation: NCz),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),9,10-bis[4-(N-carbazolyl)phenyl]anthracene (abbreviation: BCPA),3,5-bis[4-(N-carbazolyl)phenyl]biphenyl (abbreviation: BCPBi),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and thelike can be given.

In the formula, Ar represents an aromatic hydrocarbon group having 6 to42 carbon atoms, n represents a natural number of 1 to 3, and R¹ and R²represent hydrogen; an alkyl group having 1 to 4 carbon atoms; or anaryl group having 6 to 12 carbon atoms.

In the formula, Ar represents a monovalent aromatic hydrocarbon grouphaving 6 to 42 carbon atoms, and R¹ and R² represent hydrogen; an alkylgroup having 1 to 4 carbon atoms; or an aryl group having 6 to 12 carbonatoms.

In the formula, Ar represents a bivalent aromatic hydrocarbon grouphaving 6 to 42 carbon atoms, and R¹ to R⁴ represent hydrogen; an alkylgroup having 1 to 4 carbon atoms; or an aryl group having 6 to 12 carbonatoms.

However, in the formula, Ar represents a trivalent aromatic hydrocarbongroup having 6 to 42 carbon atoms, and R¹ to R⁶ represents hydrogen; analkyl group having 1 to 4 carbon atoms; or an aryl group having 6 to 12carbon atoms.

Further, it is also possible to use aromatic hydrocarbon such asanthracene, 9,10-diphenylanthracene (abbreviation: DPA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),tetracene, rubrene, or pentacene.

Although the layer 104 made of the first composite material can bemanufactured by a co-evaporation method with the above inorganiccompound and organic compound having a hole-transporting property, thelayer 104 may be formed by any of a wet method and other methods. Notethat, in the layer 104 made of the first composite material, it isdesirable that the organic compound and inorganic compound have a weightratio of 95:5 to 20:80, and preferably 90:10 to 50:50.

A semiconductor element according to the present invention which havesuch a structure has the layer 103 made of the second composite materialin a portion where the second electrode 107 is in contact with thesemiconductor layer 102; therefore, there is small energy barrier forinjecting electrons into the semiconductor layer 102 from the secondelectrode 107. In addition, the semiconductor element has the layer 104made of the first composite material in a portion where the thirdelectrode 108 is in contact with the semiconductor layer 102; therefore,there is small energy barrier for injecting holes into the semiconductorlayer 102 from the third electrode 108. Accordingly, the semiconductorelement according to the present invention can be a semiconductorelement having a low drive voltage. Moreover, in a conventionalstructure where another material is used instead of the first and secondcomposite materials for the second electrode 107 and the third electrode108, there is restriction by a work function in selecting a conductivelayer for forming the second electrode 107 and the third electrode 108,and the range of selection is extremely narrow in consideration of othercharacteristics such as conductivity or stability. On the other hand,just by providing the layer 103 made of the second composite materialand the layer 104 made of the first composite material each to be incontact with the semiconductor layer 102, in the second electrode 107and the third electrode 108 in the semiconductor element according tothe present invention, the conductive layer 105 a and the conductivelayer 105 b may have conductivity to some extent and the materialdescribed above can be used preferably; thus, the range of the selectioncan be expanded extremely widely.

Further, both the layer 104 made of the first composite material or thelayer 103 made of the second composite material can be formed by a vapordeposition method or a wet method, and it is also possible tomanufacture a semiconductor element according to the present inventionsimply and easily.

Furthermore, in the semiconductor element according to the presentinvention, electrons are injected into the semiconductor layer 102 fromthe second electrode 107 and the holes are injected into thesemiconductor layer 102 from the third electrode 108 by an electricfield generated by applying voltage above a certain level so thatvoltage on the third electrode side gets higher than that on the secondelectrode side between the second electrode 107 and the third electrode108. The injected holes and electrons are recombined in thesemiconductor layer 102, molecules in the semiconductor layer 102 areexcited, and thus, light emission can be obtained from the semiconductorlayer 102 upon the excited molecules returning to a ground state. Atthis time, the injection amount of electrons or holes can be changedwithout changing current or voltage that is applied between the secondelectrode 107 and the third electrode 108 by applying voltage to thefirst electrode 100 and changing the voltage; therefore, it is possibleto control light emission.

In addition, since it is possible to control light emission withoutproviding a driving transistor and a light-emitting element separately,an aperture ratio is improved, which is advantageous in high resolution.Moreover, since the number of manufacturing processes is small, alight-emitting device according to the present invention provided with afunction for controlling a semiconductor element, or an organictransistor or an organic light-emitting transistor according to thepresent invention can have few incidence of a defective product with theuse thereof; thus, a light-emitting device in a preferable yield can beobtained.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 1B. The semiconductor elementaccording to the present invention illustrated in FIG. 1B includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film which is not shown, and theinsulating film 101 electrically insulates the semiconductor layer 102and the first electrode 100. In addition, the second electrode 107 isformed of two layers of a conductive layer 105 a and a layer 103 made ofa second composite material, and the third electrode 108 is formed oftwo layers of a conductive layer 105 b and a layer 104 made of a firstcomposite material, respectively. The layer 103 made of the secondcomposite material in the second electrode 107 and the layer 104 made ofthe first composite material in the third electrode 108 are provided sothat at least parts thereof are in contact with the semiconductor layer102. The conductive layer 105 a and the conductive layer 105 b areformed inside enough that each of peripheries thereof does not reachperipheries of the layer 103 made of the second composite material andthe layer 104 made of the first composite material. In other words, thesemiconductor element in FIG. 1B is different from that in FIG. 1A, andthe layer 103 made of the second composite material, the layer 104 madeof the first composite material, the conductive layer 105 a, and theconductive layer 105 b are each formed so as to be in contact with thesemiconductor layer 102. Therefore, the layer 103 made of the secondcomposite material and the layer 104 made of the first compositematerial are formed so as to cover the surface of the conductive layer105 a and the conductive layer 105 b.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 1B is thesame as those in FIG. 1A; therefore, the illustration in FIG. 1B followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 1C. The semiconductor elementaccording to the present invention illustrated in FIG. 1C includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film which is not shown, and theinsulating film 101 electrically insulates the semiconductor layer 102and the first electrode 100. In addition, the second electrode 107 isformed of two layers of a conductive layer 105 a and a layer 103 made ofa second composite material, and the third electrode 108 is formed oftwo layers of a conductive layer 105 b and a layer 104 made of a firstcomposite material, respectively. The layer 103 made of the secondcomposite material in the second electrode 107 and the layer 104 made ofthe first composite material in the third electrode 108 are provided soas to be in contact with the semiconductor layer 102. The conductivelayer 105 a and the conductive layer 105 b are formed inside enough thateach of peripheries thereof does not reach peripheries of the layer 103made of the second composite material and the layer 104 made of thefirst composite material, and the conductive layers are not in contactwith the semiconductor layer 102. In other words, as well as in FIG. 1A,the conductive layer 105 a and the conductive layer 105 b are not incontact with the semiconductor layer 102 in the semiconductor element inFIG. 1C. The conductive layer 105 a is formed so that a width thereof (alength in a channel length direction 109) gets shorter than a width ofthe layer 103 made of the second composite material (the length in thechannel length direction 109), which is different from FIG. 1A. Inaddition, the conductive layer 105 b is also formed so that a widththereof (the length in the channel length direction 109) gets shorterthan a width of the layer 104 made of the first composite material (thelength in the channel direction 109).

In the case where the electrode is disposed over the semiconductor layer102 as illustrated in FIGS. 1A to 1C, the surface of the semiconductorlayer 102 is damaged in forming the electrode; thus, a performance as asemiconductor element is deteriorated in some cases. However, in such astructure as FIG. 1C, the conductive layer 105 a and the conductivelayer 105 b are formed inside enough that each of peripheries thereofdoes not reach peripheries of the layer 103 made of the second compositematerial and the layer 104 made of the first composite material, and theconductive layers are not in contact with the semiconductor layer 102.Therefore, it becomes possible to form a metal conductive layer withoutdamaging the semiconductor layer 102. Specifically, the conductivelayers may be formed only over the layers made of the compositematerials with the use of a mask.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 1C is thesame as those in FIG. 1A; therefore, the illustration in FIG. 1C followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 2A. The semiconductor elementaccording to the present invention illustrated in FIG. 2A includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film, which is not shown, and theinsulating film 101 electrically insulates the first electrode 100 fromthe semiconductor layer 102, the second electrode 107, and the thirdelectrode 108. The second electrode 107 and the third electrode 108 areformed in contact with the insulating film 101, and the semiconductorlayer 102 is formed to cover the insulating film 101, the secondelectrode 107, and the third electrode 108.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b may be formedinside enough that each of peripheries thereof does not reachperipheries of the layer 103 made of the second composite material andthe layer 104 made of the first composite material. In other words, theconductive layer 105 a and the conductive layer 105 b are not in contactwith the insulating film 101, and the conductive layer 105 a may beformed so that a width thereof (the length in a channel lengthdirection) gets shorter than a width of the layer 103 made of the secondcomposite material (the length in the channel length direction). Inaddition, the conductive layer 105 b may also be formed so that a widththereof (the length in the channel length direction) gets shorter than awidth of the layer 104 made of the first composite material (the lengthin the channel length direction).

In the second electrode 107 and the third electrode 108 in FIG. 2A, thelayer 103 made of the second composite material and the layer 104 madeof the first composite material are each formed closer to the firstelectrode 100, and the conductive layer 105 a and the conductive layer105 b are formed far from the insulating film 101. However, as in FIG.2C, the conductive layer 105 a and the conductive layer 105 b may beformed closer to the first electrode 100, and the layer 103 made of thesecond composite material and the layer 104 made of the first compositematerial may be formed far from the insulating film 101. In such astructure as FIG. 2C, an area where the semiconductor layer 102 and thelayer 103 made of the second composite material are in contact with eachother and an area where the layer 104 made of the first compositematerial and the semiconductor layer 102 are in contact with each otherget larger; therefore, FIG. 2C is a structure advantage in injectingholes and electrons. The structure in FIG. 2C is the same as that inFIG. 2A other than the order of the stacked layer of the electrodes.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIGS. 2A and2C are the same as those in FIG. 1A; therefore, the illustration inFIGS. 2A and 2C follow that in FIG. 1A and the repeated explanation willbe omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 2B. The semiconductor elementaccording to the present invention illustrated in FIG. 2B includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film, which is not shown, and theinsulating film 101 electrically insulates the first electrode 100 fromthe semiconductor layer 102, the second electrode 107, and the thirdelectrode 108. The second electrode 107 and the third electrode 108 areformed in contact with the insulating film 101, and the semiconductorlayer 102 is formed to cover the insulating film 101, the secondelectrode 107, and the third electrode 108.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b are formed insideenough that each of peripheries thereof does not reach peripheries ofthe layer 103 made of the second composite material and the layer 104made of the first composite material. In other words, the semiconductorelement in FIG. 2B is different from those in FIGS. 2A and 2C, and thelayer 103 made of the second composite material, the layer 104 made ofthe first composite material, the conductive layer 105 a, and theconductive layer 105 b are each formed so as to be in contact with theinsulating film 101. Therefore, the layer 103 made of the secondcomposite material and the layer 104 made of the first compositematerial are formed so as to cover the surface of the conductive layer105 a and the conductive layer 105 b, and the conductive layer 105 a andthe conductive layer 105 b have a structure where the conductive layersare not in contact with the semiconductor layer 102.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 2B is thesame as those in FIG. 1A; therefore, the illustration in FIG. 2B followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 3A. The semiconductor elementaccording to the present invention illustrated in FIG. 3A includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film, which is not shown, and theinsulating film 101 electrically insulates the first electrode 100 fromthe semiconductor layer 102, the second electrode 107, and the thirdelectrode 108. The second electrode 107 and the third electrode 108 areformed in contact with the insulating film 101, and the semiconductorlayer 102 is formed to cover the insulating film 101, the secondelectrode 107, and the third electrode 108.

In addition, the second electrode 107 is formed of three layers of aconductive layer 105 a, a layer 103 a made of a second compositematerial, and a layer 104 a made of a first composite material, and thethird electrode 108 is formed of three layers of a conductive layer 105b, a layer 103 b made of a second composite material, and a layer 104 bmade of a first composite material, respectively. The layer 103 a madeof the second composite material in the second electrode 107 and thelayer 104 b made of the first composite material in the third electrode108 are provided so that at least parts thereof are in contact with thesemiconductor layer 102. In addition, the layer 104 a made of the firstcomposite material and the layer 103 a made of the second compositematerial in the second electrode 107 are provided so that at least partsthereof are in contact with each other, and the layer 104 b made of thefirst composite material and the layer 103 b made of the secondcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with each other. The conductive layer105 a and the conductive layer 105 b may be formed inside enough thateach of peripheries thereof does not reach peripheries of the layersmade of these composite materials. In other words, the conductive layer105 a and the conductive layer 105 b are not in contact with theinsulating film 101, and the conductive layer 105 a may be formed sothat a width thereof (the length in a channel length direction) getsshorter than a width of the layer 103 a made of the second compositematerial (the length in the channel length direction). In addition, theconductive layer 105 b may also be formed so that a width thereof (thelength in the channel length direction) gets shorter than a width of thelayer 104 b made of the first composite material (the length in thechannel length direction).

Note that the layers 103 a and 103 b made of the second compositematerials can be formed with the material of the layer 103 made of thesecond composite material explained in FIG. 1A, and the layers 104 a and104 b made of first composite materials can be formed with the materialof the layer 104 made of the first composite material explained in FIG.1A.

In the semiconductor element according to the present inventionillustrated in FIG. 3A, the second electrode 107 and the third electrode108 each have both the layer made of the second composite material andthe layer made of the first composite material. Further, since the layermade of the second composite material and the layer made of the firstcomposite material are in contact with each other, it becomes possibleto improve injectability of electrons or holes and to reduce a drivevoltage much more.

In addition, in the structure illustrated in FIG. 3A, it is possible tomanufacture the second electrode 107 and the third electrode 108 byrepeating deposition only three times with the same mask. Therefore, itis possible to obtain a semiconductor element that can be manufacturedsimply and easily much more. Note that the order of stacking the layermade of the first composite material and the layer made of the secondcomposite material may be reversed.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 3A is thesame as those in FIG. 1A; therefore, the illustration in FIG. 3A followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 3B. The semiconductor elementaccording to the present invention illustrated in FIG. 3B includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film, which is not shown, and theinsulating film 101 electrically insulates the first electrode 100 fromthe semiconductor layer 102, the second electrode 107, and the thirdelectrode 108. The second electrode 107 and the third electrode 108 areformed in contact with the insulating film 101, and the semiconductorlayer 102 is formed to cover the insulating film 101, the secondelectrode 107, and the third electrode 108.

In addition, the second electrode 107 is formed of three layers of aconductive layer 105 a, a layer 103 a made of a second compositematerial, and a layer 104 a made of a first composite material, and thethird electrode 108 is formed of three layers of a conductive layer 105b, a layer 103 b made of a second composite material, and a layer 104 bmade of a first composite material, respectively. The layer 103 a madeof the second composite material in the second electrode 107 and thelayer 104 b made of the first composite material in the third electrode108 are provided so that at least parts thereof are in contact with thesemiconductor layer 102. In addition, the layer 104 a made of the firstcomposite material and the layer 103 a made of the second compositematerial in the second electrode 107 are provided so that at least partsthereof are in contact with each other, and the layer 104 b made of thefirst composite material and the layer 103 b made of the secondcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with each other. The conductive layer105 a and the conductive layer 105 b may be formed inside enough thateach of peripheries thereof does not reach peripheries of the layersmade of these composite materials. In other words, the conductive layer105 a and the conductive layer 105 b are not in contact with theinsulating film 101, and the conductive layer 105 a may be formed sothat a width thereof (the length in a channel length direction) getsshorter than a width of the layer 103 a made of the second compositematerial (the length in the channel length direction). In addition, theconductive layer 105 b may also be formed so that a width thereof (thelength in the channel length direction) gets shorter than a width of thelayer 104 b made of the first composite material (the length in thechannel length direction).

Note that the layers 103 a and 103 b made of the second compositematerials can be formed with the material of the layer 103 made of thesecond composite material explained in FIG. 1A, and the layers 104 a and104 b made of first composite materials can be formed with the materialof the layer 104 made of the first composite material explained in FIG.1A.

In the semiconductor element according to the present inventionillustrated in FIG. 3B, the second electrode 107 and the third electrode108 each have both the layer made of the second composite material andthe layer made of the first composite material. Further, since the layermade of the second composite material and the layer made of the firstcomposite material are in contact with each other, it becomes possibleto improve injectability of electrons or holes and to reduce a drivevoltage much more. Note that, in the semiconductor element according tothe present invention illustrated in FIG. 3B, a portion where the layer103 a made of the second composite material is in contact with thesemiconductor layer 102 is placed closer to the third electrode 108 sidethan the layer 104 a made of the first composite material in the secondelectrode 107 on the side for injecting electrons. In the thirdelectrode 108 on the side for injecting holes, a portion where the layer104 b made of the first composite material is in contact with thesemiconductor layer 102 is placed closer to the second electrode 107side than the layer 103 b made of the second composite material.Therefore, it is considered that recombination possibility or injectionefficiency is improved, which is a preferable structure.

In addition, in the structure illustrated in FIG. 3B, it is possible tomanufacture the second electrode 107 and the third electrode 108 onlywith the second layer and the third layer deposited by slightly movingthe same mask after depositing the first layer, among the three layersof the second electrode 107 and the third electrode 108. Therefore, itis possible to obtain a semiconductor element that can be manufacturedsimply and easily much more. Note that the order of stacking the layermade of the first composite material and the layer made of the secondcomposite material may be reversed. However, the shape of the secondelectrode 107 and the third electrode 108 are also reversed so that aportion where the layer 103 a made of the second composite material isin contact with the semiconductor layer 102 is placed closer to thethird electrode 108 side than the layer 104 a made of the firstcomposite material in the second electrode 107 on the side for injectingelectrons, and, in the third electrode 108 on the side for injectingholes, a portion where the layer 104 b made of the first compositematerial is in contact with the semiconductor layer 102 is placed closerto the second electrode 107 side than the layer 103 b made of the secondcomposite material.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 3B is thesame as those in FIG. 1A; therefore, the illustration in FIG. 3B followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 3C. The semiconductor elementaccording to the present invention illustrated in FIG. 3C includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The first electrode 100 is formed over an arbitrary insulator such as aninsulating substrate or an insulating film, which is not shown, and theinsulating film 101 electrically insulates the first electrode 100 fromthe semiconductor layer 102, the second electrode 107, and the thirdelectrode 108. The second electrode 107 and the third electrode 108 areformed in contact with the insulating film 101, and the semiconductorlayer 102 is formed to cover the insulating film 101, the secondelectrode 107, and the third electrode 108.

In addition, the second electrode 107 is formed of three layers of aconductive layer 105 a, a layer 103 a made of a second compositematerial, and a layer 104 a made of a first composite material, and thethird electrode 108 is formed of three layers of a conductive layer 105b, a layer 103 b made of a second composite material, and a layer 104 bmade of a first composite material, respectively. The layer 103 a madeof the second composite material in the second electrode 107 and thelayer 104 b made of the first composite material in the third electrode108 are provided so that at least parts thereof are in contact with thesemiconductor layer 102. In addition, the layer 104 a made of the firstcomposite material and the layer 103 a made of the second compositematerial in the second electrode 107 are provided so that at least partsthereof are in contact with each other, and the layer 104 b made of thefirst composite material and the layer 103 b made of the secondcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with each other. The conductive layer105 a and the conductive layer 105 b may be formed inside enough thateach of peripheries thereof does not reach peripheries of the layersmade of these composite materials. In other words, the conductive layer105 a and the conductive layer 105 b are not in contact with theinsulating film 101, and the conductive layer 105 a may be formed sothat a width thereof (the length in a channel length direction) getsshorter than a width of the layer 103 a made of the second compositematerial (the length in the channel length direction). In addition, theconductive layer 105 b may also be formed so that a width thereof (thelength in the channel length direction) gets shorter than a width of thelayer 104 b made of the first composite material (the length in thechannel length direction).

Note that the layers 103 a and 103 b made of the second compositematerials can be formed with the material of the layer 103 made of thesecond composite material explained in FIG. 1A, and the layers 104 a and104 b made of first composite materials can be formed with the materialof the layer 104 made of the first composite material explained in FIG.1A.

In the semiconductor element according to the present inventionillustrated in FIG. 3C, the second electrode 107 and the third electrode108 each have both the layer made of the second composite material andthe layer made of the first composite material. Further, since the layermade of the second composite material and the layer made of the firstcomposite material are in contact with each other, it becomes possibleto improve injectability of electrons or holes and to reduce a drivevoltage much more. Note that, in the semiconductor element according tothe present invention illustrated in FIG. 3B, a portion where the layer103 a made of the second composite material is in contact with thesemiconductor layer 102 is placed closer to the third electrode 108 sidethan the layer 104 a made of the first composite material in the secondelectrode 107 on the side for injecting electrons. In the thirdelectrode 108 on the side for injecting holes, a portion where the layer104 b made of the first composite material is in contact with thesemiconductor layer 102 is placed closer to the second electrode 107side than the layer 103 b made of the second composite material.Therefore, it is considered that recombination possibility or injectionefficiency is improved, which is a preferable structure. Note that theorder of stacking the layer made of the first composite material and thelayer made of the second composite material may be reversed. However,the shape of the second electrode 107 and the third electrode 108 arealso reversed so that a portion where the layer 103 a made of the secondcomposite material is in contact with the semiconductor layer 102 isplaced closer to the third electrode 108 side than the layer 104 a madeof the first composite material in the second electrode 107 on the sidefor injecting electrons, and, in the third electrode 108 on the side forinjecting holes, a portion where the layer 104 b made of the firstcomposite material is in contact with the semiconductor layer 102 isplaced closer to the second electrode 107 side than the layer 103 b madeof the second composite material.

FIG. 3D, having a comb-shape electrode as shown in FIG. 4, is anapplication example of FIG. 3C and an example of applying thesemiconductor element the shape of which is in FIG. 3C in a case of astructure where many semiconductor elements are connected. FIG. 3Dcorresponds to a cross-sectional view taken along α-β in FIG. 4. In thisstructure, the third electrode 108 exists on the both sides of thesecond electrode 107 and light emission can be obtained through thesemiconductor layer 102 on either side. In addition, light emission canbe controlled separately by the first electrodes 100 providedseparately. Of course, the first electrode 100 may be identical.Moreover, although not shown, the third electrode 108 is provided on theboth sides of the second electrode 107, and FIG. 3D is a structure wheresuch a structure is provided repeatedly.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 3C is thesame as those in FIG. 1A; therefore, the illustration in FIG. 3C followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 5A. The semiconductor elementaccording to the present invention illustrated in FIG. 5A includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The semiconductor layer 102 is formed over an arbitrary insulator suchas an insulating substrate or an insulating film, which is not shown,and the insulating film 101 electrically insulates the first electrode100 from the semiconductor layer 102, the second electrode 107, and thethird electrode 108. The second electrode 107 and the third electrode108 are formed over the semiconductor layer 102, and the insulating film101 is formed to cover the semiconductor layer 102, the second electrode107, and the third electrode 108.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b may be formedinside enough that each of peripheries thereof does not reachperipheries of the layer 103 made of the second composite material andthe layer 104 made of the first composite material. In other words, theconductive layer 105 a and the conductive layer 105 b are not in contactwith the semiconductor layer 102, and the conductive layer 105 a may beformed so that a width thereof (the length in a channel lengthdirection) gets shorter than a width of the layer 103 a made of thesecond composite material (the length in the channel length direction).In addition, the conductive layer 105 b may also be formed so that awidth thereof (the length in the channel length direction) gets shorterthan a width of the layer 104 b made of the first composite material(the length in the channel length direction).

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 5A is thesame as those in FIG. 1A; therefore, the illustration in FIG. 5A followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 5B. The semiconductor elementaccording to the present invention illustrated in FIG. 5B includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The semiconductor layer 102 is formed over an arbitrary insulator suchas an insulating substrate or an insulating film, which is not shown,and the insulating film 101 electrically insulates the first electrode100 from the semiconductor layer 102, the second electrode 107, and thethird electrode 108. The second electrode 107 and the third electrode108 are formed over the semiconductor layer 102, and the insulating film101 is formed to cover the semiconductor layer 102, the second electrode107, and the third electrode 108.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b are formed insideenough that each of peripheries thereof does not reach peripheries ofthe layer 103 made of the second composite material and the layer 104made of the first composite material. In other words, the semiconductorelement in FIG. 5B is different from that in FIG. 5A, and the layer 103made of the second composite material, the layer 104 made of the firstcomposite material, the conductive layer 105 a, and the conductive layer105 b are each formed so as to be in contact with the semiconductorlayer 102. Therefore, the layer 103 made of the second compositematerial and the layer 104 made of the first composite material areformed so as to cover the surface of the conductive layer 105 a and theconductive layer 105 b, and the conductive layer 105 a and theconductive layer 105 b have a structure where the conductive layers arenot in contact with the insulating film 101.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 5B is thesame as those in FIG. 1A; therefore, the illustration in FIG. 5B followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 5C. The semiconductor elementaccording to the present invention illustrated in FIG. 5C includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The semiconductor layer 102 is formed over an arbitrary insulator suchas an insulating substrate or an insulating film, which is not shown,and the insulating film 101 electrically insulates the first electrode100 from the semiconductor layer 102, the second electrode 107, and thethird electrode 108. The second electrode 107 and the third electrode108 are formed over the semiconductor layer 102, and the insulating film101 is formed to cover the semiconductor layer 102, the second electrode107, and the third electrode 108.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b are formed insideenough that each of peripheries thereof does not reach peripheries ofthe layer 103 made of the second composite material and the layer 104made of the first composite material, and the conductive layers are notin contact with the semiconductor layer 102. In other words, theconductive layer 105 a and the conductive layer 105 b are not in contactwith the semiconductor layer 102, and the conductive layer 105 a isformed so that a width thereof (the length in a channel lengthdirection) gets shorter than a width of the layer 103 a made of thesecond composite material (the length in the channel length direction).In addition, the conductive layer 105 b is also formed so that a widththereof (the length in the channel length direction) gets shorter than awidth of the layer 104 b made of the first composite material (thelength in the channel length direction).

In the case where the electrode is disposed over the semiconductor layer102 as illustrated in FIGS. 5A to 5C, the surface of the semiconductorlayer 102 is damaged by sputtering in forming the electrode; thus, aperformance as a semiconductor element is deteriorated in some cases.However, in such a structure as FIG. 5C, the conductive layer 105 a andthe conductive layer 105 b are formed inside enough that each ofperipheries thereof does not reach peripheries of the layer 103 made ofthe second composite material and the layer 104 made of the firstcomposite material, and the conductive layers are not in contact withthe semiconductor layer 102. Therefore, it becomes possible to form ametal conductive layer without damaging the semiconductor layer 102.Specifically, the conductive layers may be formed only over the layersmade of the composite materials with the use of a mask.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 5C is thesame as those in FIG. 1A; therefore, the illustration in FIG. 5C followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 6B. The semiconductor elementaccording to the present invention illustrated in FIG. 6B includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The second electrode 107 and the third electrode 108 are formed over anarbitrary insulator such as an insulating substrate or an insulatingfilm, which is not shown. The semiconductor layer 102 is formed to coverthe second electrode 107 and the third electrode 108, and the insulatingfilm 101 electrically insulates the first electrode 100 from thesemiconductor layer 102.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b may be formedinside enough that each of peripheries thereof does not reachperipheries of the layer 103 made of the second composite material andthe layer 104 made of the first composite material. In other words, theconductive layer 105 a may be formed so that a width thereof (the lengthin a channel length direction) gets shorter than a width of the layer103 a made of the second composite material (the length in the channellength direction). In addition, the conductive layer 105 b may also beformed so that a width thereof (the length in the channel lengthdirection) gets shorter than a width of the layer 104 b made of thefirst composite material (the length in the channel length direction).

In the second electrode 107 and the third electrode 108 in FIG. 6B, thelayer 103 made of the second composite material and the layer 104 madeof the first composite material are each formed closer to the firstelectrode 100, and the conductive layer 105 a and the conductive layer105 b are formed far from the insulating film 101. However, as in FIG.6A, the conductive layer 105 a and the conductive layer 105 b may beformed closer to the first electrode 100, and the layer 103 made of thesecond composite material and the layer 104 made of the first compositematerial may be formed far from the insulating film 101. In such astructure as FIG. 6B, an area where the semiconductor layer 102 and thelayer 103 made of the second composite material are in contact with eachother and an area where the layer 104 made of the first compositematerial and the semiconductor layer 102 are in contact with each otherget larger; therefore, FIG. 6B is a structure advantage in injectingholes and electrons. The structure in FIG. 6B is the same as that inFIG. 6A other than the order of the stacked layer of the electrodes.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIGS. 6A and6B are the same as those in FIG. 1A; therefore, the illustration inFIGS. 6A and 6B follows that in FIG. 1A and the repeated explanationwill be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 6C. The semiconductor elementaccording to the present invention illustrated in FIG. 6C includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The second electrode 107 and the third electrode 108 are formed over anarbitrary insulator such as an insulating substrate or an insulatingfilm, which is not shown. The semiconductor layer 102 is formed to coverthe second electrode 107 and the third electrode 108, and the insulatingfilm 101 electrically insulates the first electrode 100 from thesemiconductor layer 102.

In addition, the second electrode 107 is formed of two layers of aconductive layer 105 a and a layer 103 made of a second compositematerial, and the third electrode 108 is formed of two layers of aconductive layer 105 b and a layer 104 made of a first compositematerial, respectively. The layer 103 made of the second compositematerial in the second electrode 107 and the layer 104 made of the firstcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with the semiconductor layer 102. Theconductive layer 105 a and the conductive layer 105 b are formed insideenough that each of peripheries thereof does not reach peripheries ofthe layer 103 made of the second composite material and the layer 104made of the first composite material. In other words, the layer 103 madeof the second composite material and the layer 104 made of the firstcomposite material in the semiconductor element in FIG. 6C are formed soas to cover the surface of the conductive layer 105 a and the conductivelayer 105 b, and the conductive layer 105 a and the conductive layer 105b have a structure where the conductive layers are not in contact withthe semiconductor layer 102.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 6C is thesame as those in FIG. 1A; therefore, the illustration in FIG. 6C followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 7A. The semiconductor elementaccording to the present invention illustrated in FIG. 7A includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The second electrode 107 and the third electrode 108 are formed over anarbitrary insulator such as an insulating substrate or an insulatingfilm, which is not shown. The semiconductor layer 102 is formed to coverthe second electrode 107 and the third electrode 108, and the insulatingfilm 101 electrically insulates the first electrode 100 from thesemiconductor layer 102.

In addition, the second electrode 107 is formed of three layers of aconductive layer 105 a, a layer 103 a made of a second compositematerial, and a layer 104 a made of a first composite material, and thethird electrode 108 is formed of three layers of a conductive layer 105b, a layer 103 b made of a second composite material, and a layer 104 bmade of a first composite material, respectively. The layer 103 a madeof the second composite material in the second electrode 107 and thelayer 104 b made of the first composite material in the third electrode108 are provided so that at least parts thereof are in contact with thesemiconductor layer 102. In addition, the layer 104 a made of the firstcomposite material and the layer 103 a made of the second compositematerial in the second electrode 107 are provided so that at least partsthereof are in contact with each other, and the layer 104 b made of thefirst composite material and the layer 103 b made of the secondcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with each other. The conductive layer105 a and the conductive layer 105 b may be formed inside enough thateach of peripheries thereof does not reach peripheries of the layersmade of these composite materials. In other words, the conductive layer105 a may be formed so that a width thereof (the length in a channellength direction) gets shorter than a width of the layer 103 a made ofthe second composite material and a width of the layer 104 a made of thefirst composite material (the length in the channel length direction).In addition, the conductive layer 105 b may also be formed so that awidth thereof (the length in the channel length direction) gets shorterthan a width of the layer 103 b made of the second composite materialand a width of the layer 104 b made of the first composite material (thelength in the channel length direction).

Note that the layers 103 a and 103 b made of the second compositematerials can be formed with the material of the layer 103 made of thesecond composite material explained in FIG. 1A, and the layers 104 a and104 b made of first composite materials can be formed with the materialof the layer 104 made of the first composite material explained in FIG.1A.

In the semiconductor element according to the present inventionillustrated in FIG. 7A, the second electrode 107 and the third electrode108 each have both the layer made of the second composite material andthe layer made of the first composite material. Further, since the layermade of the second composite material and the layer made of the firstcomposite material are in contact with each other, it becomes possibleto improve injectability of electrons or holes and to reduce a drivevoltage much more.

In addition, in the structure illustrated in FIG. 7A, it is possible tomanufacture the second electrode 107 and the third electrode 108 byrepeating deposition only three times with the same mask. Therefore, itis possible to obtain a semiconductor element that can be manufacturedsimply and easily much more. Note that the order of stacking the layermade of the first composite material and the layer made of the secondcomposite material may be reversed.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 7A is thesame as those in FIG. 1A; therefore, the illustration in FIG. 7A followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 7B. The semiconductor elementaccording to the present invention illustrated in FIG. 7B includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The second electrode 107 and the third electrode 108 are formed over anarbitrary insulator such as an insulating substrate or an insulatingfilm, which is not shown. The semiconductor layer 102 is formed to coverthe second electrode 107 and the third electrode 108, and the insulatingfilm 101 electrically insulates the first electrode 100 from thesemiconductor layer 102.

In addition, the second electrode 107 is formed of three layers of aconductive layer 105 a, a layer 103 a made of a second compositematerial, and a layer 104 a made of a first composite material, and thethird electrode 108 is formed of three layers of a conductive layer 105b, a layer 103 b made of a second composite material, and a layer 104 bmade of a first composite material, respectively. The layer 103 a madeof the second composite material in the second electrode 107 and thelayer 104 b made of the first composite material in the third electrode108 are provided so that at least parts thereof are in contact with thesemiconductor layer 102. In addition, the layer 104 a made of the firstcomposite material and the layer 103 a made of the second compositematerial in the second electrode 107 are provided so that at least partsthereof are in contact with each other, and the layer 104 b made of thefirst composite material and the layer 103 b made of the secondcomposite material in the third electrode 108 are provided so that atleast parts thereof are in contact with each other. The conductive layer105 a and the conductive layer 105 b may be formed inside enough thateach of peripheries thereof does not reach peripheries of the layersmade of these composite materials. In other words, the conductive layer105 a may be formed so that a width thereof (the length in a channellength direction) gets shorter than a width of the layer 103 a made ofthe second composite material (the length in the channel lengthdirection). In addition, the conductive layer 105 b may also be formedso that a width thereof (the length in the channel length direction)gets shorter than a width of the layer 103 b made of the secondcomposite material (the length in the channel length direction).

Note that the layers 103 a and 103 b made of the second compositematerials can be formed with the material of the layer 103 made of thesecond composite material explained in FIG. 1A, and the layers 104 a and104 b made of first composite materials can be formed with the materialof the layer 104 made of the first composite material explained in FIG.1A.

In the semiconductor element according to the present inventionillustrated in FIG. 7B, the second electrode 107 and the third electrode108 each have both the layer made of the second composite material andthe layer made of the first composite material. Further, since the layermade of the second composite material and the layer made of the firstcomposite material are in contact with each other, it becomes possibleto improve injectability of electrons or holes and to reduce a drivevoltage much more. Note that, in the semiconductor element according tothe present invention illustrated in FIG. 7B, a portion where the layer103 a made of the second composite material is in contact with thesemiconductor layer 102 is placed closer to the third electrode 108 sidethan the layer 104 a made of the first composite material in the secondelectrode 107 on the side for injecting electrons. In the thirdelectrode 108 on the side for injecting holes, a portion where the layer104 b made of the first composite material is in contact with thesemiconductor layer 102 is placed closer to the second electrode 107side than the layer 103 b made of the second composite material.Therefore, it is considered that recombination possibility or injectionefficiency is improved, which is a preferable structure.

In addition, in the structure illustrated in FIG. 7B, it is possible tomanufacture the second electrode 107 and the third electrode 108 onlywith the second layer and the third layer deposited by slightly movingthe same mask after depositing the first layer, among the three layersof the second electrode 107 and the third electrode 108. Therefore, itis possible to obtain a semiconductor element that can be manufacturedsimply and easily much more. Note that the order of stacking the layermade of the first composite material and the layer made of the secondcomposite material may be reversed. However, the shape of the secondelectrode 107 and the third electrode 108 are also reversed so that aportion where the layer 103 a made of the second composite material isin contact with the semiconductor layer 102 is placed closer to thethird electrode 108 side than the layer 104 a made of the firstcomposite material in the second electrode 107 on the side for injectingelectrons, and, in the third electrode 108 on the side for injectingholes, a portion where the layer 104 b made of the first compositematerial is in contact with the semiconductor layer 102 is placed closerto the second electrode 107 side than the layer 103 b made of the secondcomposite material.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 7B is thesame as those in FIG. 1A; therefore, the illustration in FIG. 7B followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIG. 7C. The semiconductor elementaccording to the present invention illustrated in FIG. 7C includes afirst electrode 100, an insulating film 101, a semiconductor layer 102,a second electrode 107, and a third electrode 108.

The second electrode 107 and the third electrode 108 are formed over anarbitrary insulator such as an insulating substrate or an insulatingfilm, which is not shown. The semiconductor layer 102 is formed to coverthe second electrode 107 and the third electrode 108, and the insulatingfilm 101 electrically insulates the first electrode 100 from thesemiconductor layer 102.

In addition, the second electrode 107 is formed of three layers of aconductive layer 105 a, a layer 103 a made of a second compositematerial, and a layer 104 a made of the first composite material, andthe third electrode 108 is formed of three layers of a conductive layer105 b, a layer 103 b made of a second composite material, and a layer104 b made of a first composite material, respectively. The layer 103 amade of the second composite material in the second electrode 107 andthe layer 104 b made of the first composite material in the thirdelectrode 108 are provided so that at least parts thereof are in contactwith the semiconductor layer 102. In addition, the layer 104 a made ofthe first composite material and the layer 103 a made of the secondcomposite material in the second electrode 107 are provided so that atleast parts thereof are in contact with each other, and the layer 104 bmade of the first composite material and the layer 103 b made of thesecond composite material in the third electrode 108 are provided sothat at least parts thereof are in contact with each other. Theconductive layer 105 a and the conductive layer 105 b may be formedinside enough that each of peripheries thereof does not reachperipheries of the layers made of these composite materials. In otherwords, the conductive layer 105 a may be formed so that a width thereof(the length in a channel length direction) gets shorter than a width ofthe layer 103 a made of the second composite material (the length in thechannel length direction). In addition, the conductive layer 105 b mayalso be formed so that a width thereof (the length in the channel lengthdirection) gets shorter than a width of the layer 103 b made of thesecond composite material (the length in the channel length direction).

Note that the layers 103 a and 103 b made of the second compositematerials can be formed with the material of the layer 103 made of thesecond composite material explained in FIG. 1A, and the layers 104 a and104 b made of first composite materials can be formed with the materialof the layer 104 made of the first composite material explained in FIG.1A.

In the semiconductor element according to the present inventionillustrated in FIG. 7C, the second electrode 107 and the third electrode108 each have both the layer made of the second composite material andthe layer made of the first composite material. Further, since the layermade of the second composite material and the layer made of the firstcomposite material are in contact with each other, it becomes possibleto improve injectability of electrons or holes and to reduce a drivevoltage much more. Note that, in the semiconductor element according tothe present invention illustrated in FIG. 7B, a portion where the layer103 a made of the second composite material is in contact with thesemiconductor layer 102 is placed closer to the third electrode 108 sidethan the layer 104 a made of the first composite material in the secondelectrode 107 on the side for injecting electrons. In the thirdelectrode 108 on the side for injecting holes, a portion where the layer104 b made of the first composite material is in contact with thesemiconductor layer 102 is placed closer to the second electrode 107side than the layer 103 b made of the second composite material.Therefore, it is considered that recombination possibility or injectionefficiency is improved, which is a preferable structure. Note that theorder of stacking the layer made of the first composite material and thelayer made of the second composite material may be reversed. However,the shape of the second electrode 107 and the third electrode 108 arealso reversed so that a portion where the layer 103 a made of the secondcomposite material is in contact with the semiconductor layer 102 isplaced closer to the third electrode 108 side than the layer 104 a madeof the first composite material in the second electrode 107 on the sidefor injecting electrons, and, in the third electrode 108 on the side forinjecting holes, a portion where the layer 104 b made of the firstcomposite material is in contact with the semiconductor layer 102 isplaced closer to the second electrode 107 side than the layer 103 b madeof the second composite material.

FIG. 7D, having a comb-shape electrode as shown in FIG. 4, is anapplication example of FIG. 7C and an example of applying thesemiconductor element the shape of which is in FIG. 7C in a case of astructure where many semiconductor elements are connected. FIG. 7Dcorresponds to a cross-sectional view taken along α-β in FIG. 4. In thisstructure, the third electrode 108 exists on the both sides of thesecond electrode 107 and light emission can be obtained through thesemiconductor layer 102 on either side. In addition, except the firstelectrode 100, light emission can be controlled separately. Of course,the first electrode 100 may be identical. Moreover, although not shown,the third electrode 108 is provided on the both sides of the secondelectrode 107, and FIG. 7D is a structure where such a structure isprovided repeatedly.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIG. 7C is thesame as those in FIG. 1A; therefore, the illustration in FIG. 7C followsthat in FIG. 1A and the repeated explanation will be omitted.

A semiconductor element according to the present invention havingdifferent structure is shown in FIGS. 8A to 8D. The semiconductorelement according to the present invention illustrated in FIGS. 8A to 8Dincludes a first electrode 100, an insulating film 101, a semiconductorlayer 102, a second electrode 107, and a third electrode 108.

In the structures of FIGS. 8A to 8D, the structures of FIGS. 8A to 8Dare almost the same as those of FIG. 1A, FIG. 2A, FIG. 5A, and FIG. 6A,respectively. However, the second electrode 107 has a three-layerstructure of a layer 103 made of a second composite material, a layer104 a made of a first composite material, and a conductive layer 105 a.FIGS. 8A to 8D differ from FIG. 1A, FIG. 2A, FIG. 5A, and FIG. 6A,respectively, in that the layer 103 made of the second compositematerial and the layer 104 a made of the first composite material are incontact with each other.

In the second electrode 107, a stacked layer structure of the layer 103made of the second composite material and the layer 104 a made of thefirst composite material is included. Therefore, it is possible toobtain a semiconductor element in which electrons are easily injectedinto the semiconductor layer 102 from the layer 103 made of the secondcomposite material and a drive voltage is decreased much more.

Note that, in FIGS. 8A to 8D, only drawings corresponding to FIG. 1A,FIG. 2A, FIG. 5A, and FIG. 6A are shown; however, the structures inFIGS. 8A to 8D can be appropriately applied to the semiconductor elementaccording to the present invention each illustrated in FIGS. 1A to 1C,FIGS. 2A to 2C, FIGS. 5A to 5C, and FIGS. 6A to 6C.

Note that the other structure, material, and effect of the semiconductorelement according to the present invention illustrated in FIGS. 8A to 8Dare the same as those in FIG. 1A; therefore, the illustration in FIGS.8A to 8D follows that in FIG. 1A and the repeated explanation will beomitted.

Each of the semiconductor elements in FIGS. 1A to 1C, FIGS. 2A to 2C,FIGS. 3A to 3D, FIG. 4, FIGS. 5A to 5C, FIGS. 6A to 6C, FIGS. 7A to 7D,and FIGS. 8A to 8D is an organic transistor where the first electrode100 is a gate electrode, one of the second electrode 107 and the thirdelectrode 108 is a source electrode, and the other is a drain electrode.In addition, since light emission can be obtained through thesemiconductor layer 102, the semiconductor element can also be referredto as an organic light-emitting transistor.

Which of an electron and a hole is a main carrier determines whetherthis organic transistor or organic light-emitting transistor is a p-typetransistor or an n-channel transistor. Therefore, in a case of a p-typeorganic transistor or organic light-emitting transistor according to thepresent invention, of the second electrode 107 and the third electrode108, the electrode for applying higher voltage is referred to as asource electrode and the other electrode for applying lower voltage isreferred to as a drain electrode in driving the electrodes. In a case ofan n-type organic transistor or organic light-emitting transistoraccording to the present invention, of the second electrode 107 and thethird electrode 108, the electrode for applying lower voltage isreferred to as a source electrode and the other electrode for applyinghigher voltage is referred to as a drain electrode in driving theelectrodes.

The p-type organic transistor or organic light-emitting transistor has astructure where the source electrode at least includes a layer made of afirst composite material and the layer made of the first compositematerial in the source electrode is in contact with the semiconductorlayer 102, and the drain electrode at least includes a layer made of asecond composite material and the layer made of the second compositematerial in the drain electrode is in contact with the semiconductorlayer 102. In addition, the n-type organic transistor or organiclight-emitting transistor has a structure where the source electrode atleast includes a layer made of a second composite material and the layermade of the second composite material in the source electrode is incontact with the semiconductor layer 102, and the drain electrode atleast includes a layer made of a first composite material and the layermade of the first composite material in the drain electrode is incontact with the semiconductor layer 102.

Embodiment Mode 2

A semiconductor element according to the present invention having astructure different from those in FIGS. 1A to 1C, FIGS. 2A to 2C, FIGS.3A to 3D, FIGS. 5A to 5C, FIGS. 6A to 6C, FIGS. 7A to 7D, and FIGS. 8Ato 8D will be explained with reference to FIGS. 9A to 9C, FIGS. 10A to10C, FIGS. 11A to 11C, and FIGS. 12A to 12C.

A semiconductor element according to the present invention each shown inFIGS. 9A to 9C includes a first electrode 100, an insulating film 101, alayer 106 e having an electron-transporting property, a second electrode107, a third electrode 108, and a semiconductor layer 102 and, in thebasic structure, FIG. 9A, FIG. 9B, and FIG. 9C correspond to FIG. 2A,FIG. 3B, and FIG. 8B, respectively. The different portion in eachcorresponding structure is that the layer 106 e having anelectron-transporting property is formed between the insulating film 101and each of the second electrode 107, the third electrode 108, and thesemiconductor layer 102.

In any of structures in FIGS. 9A to 9C, in the second electrode 107, alayer 103 or 103 a made of a second composite material is formed to bein contact at least with the layer 106 e having an electron-transportingproperty, and, in the third electrode 108, a layer 104 or 104 b made ofa first composite material is formed to be in contact at least with thesemiconductor layer 102.

In the semiconductor elements according to the present invention havingsuch a structure, electrons are injected into the layer 106 e having anelectron-transporting property from the second electrode 107 and holesare injected into the semiconductor layer 102 from the third electrode108 when voltage above a certain level is applied between the secondelectrode 107 and the third electrode 108 so that the voltage of thethird electrode 108 gets higher. By having such a structure, electronsare injected into the layer 106 e having an electron-transportingproperty even when the electron-transporting property of thesemiconductor layer 102 is small. Therefore, further, it is alsopossible to improve injectability or transportability of holes andelectrons and to reduce a drive voltage. The molecules of thesemiconductor layer 102 are excited as a result of recombining theinjected electrons and holes, and light emission can be obtained uponthe excited molecules returning to a ground state.

As the material of the layer 106 e having an electron-transportingproperty, the following material having a comparatively highelectron-transporting property is used: a metal complex such astris(8-quinolinolato)aluminum (abbreviation: Alq₃);tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃);bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂);bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq); bis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp₂);bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂); orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)₂), anoxadiazole derivative such as2-(4-biphenylyl)-5-(4-tert-buthylphenyl)-1,3,4-oxadiazole (abbreviation:PBD) or 1,3-bis[5-(p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7), a triazole derivative such as3-(4-biphenylyl)-4-phenyl-5-(4-tert-buthylphenyl)-1,2,4-triazole(abbreviation: TAZ) or3-(4-biphenylyl)-4-(4-ethylpheyl)-5-(4-tert-buthylphenyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproin (abbreviation: BCP),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), 4,4-bis(5-methylbenzoxazol-2-yl)stilbene(abbreviation: BzOs), or the like. In the structures of FIGS. 9A to 9C,the materials described in Embodiment Mode 1 can be used as the materialof the semiconductor layer 102; however, the structures in FIGS. 9A to9C are effective especially when the material having a hole-transportingproperty is used as a material generally said as a p-type semiconductoror a host material. Note that, in order to recombine holes and electronseasily, it is desirable to select as small as possible the combinationof an energy barrier of the layer 106 e having an electron-transportingproperty and the semiconductor layer 102.

The other structures and effects thereof in FIG. 9A, FIG. 9B, and FIG.9C are the same as those in FIG. 2A, FIG. 3B, and FIG. 8B, respectively;therefore, the repeated explanation will be omitted. Refer to theexplanation of each corresponding drawing. Note that, although only FIG.2A in FIGS. 2A to 2C and only FIG. 3B in FIG. 3A to 3D are given as anexample for explanation, it is possible to apply the structures of FIGS.9A to 9C to FIG. 2B, FIG. 3C, and FIG. 3D.

A semiconductor element according to the present invention each shown inFIGS. 10A to 10C includes a first electrode 100, an insulating film 101,a layer 106 h having a hole-transporting property, a second electrode107, a third electrode 108, and a semiconductor layer 102 and, in thebasic structure, FIGS. 10A, 10B, and 10C correspond to FIG. 2A, FIG. 3B,and FIG. 8B, respectively. The different portion in each correspondingstructure is that the layer 106 h having a hole-transporting property isformed between the insulating film 101 and each of the second electrode107, the third electrode 108, and the semiconductor layer 102.

In any of structures in FIGS. 10A to 10C, in the second electrode 107, alayer 103 or 103 a made of a second composite material is formed to bein contact at least with the semiconductor layer 102, and, in the thirdelectrode 108, a layer 104 or 104 b made of a first composite materialis formed to be in contact at least with the layer 106 h having ahole-transporting property.

In the semiconductor elements according to the present invention havingsuch a structure, electrons are injected into the semiconductor layer102 from the second electrode 107 and holes are injected into the layer106 h having a hole-transporting property from the third electrode 108when voltage above a certain level is applied between the secondelectrode 107 and the third electrode 108 so that the voltage of thethird electrode 108 gets higher. By having such a structure, lightemission can be obtained without applying a large electric field evenwhen the hole-transporting property of the semiconductor layer 102 issmall. In addition, since injectability or transportability of holes andelectrons can also be improved, it also becomes possible to reduce adrive voltage. The molecules of the semiconductor layer 102 are excitedas a result of recombining the injected electrons and holes, and lightemission can be obtained upon the excited molecules returning to aground state.

As the material of the layer 106 h having a hole-transporting property,the following material having a comparatively high hole-transportingproperty is used: 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB), 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl(abbreviation: TPD), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl(abbreviation: DNTPD), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), phthalocyanine (abbreviation: H₂ Pc), copperphthalocyanine (CuPc), vanadyl phthalocyanine (abbreviation: VOPc), orthe like. In the structures of FIGS. 10A to 10C, the materials describedin Embodiment Mode 1 can be used as the material of the semiconductorlayer 102; however, the structures in FIGS. 10A to 10C are effectiveespecially when the material having an electron-transporting property isused as a material generally said as a p-type semiconductor or a hostmaterial. Note that, in order to recombine holes and electrons easily,it is desirable to select as small as possible the combination of anenergy barrier of the layer 106 h having a hole-transporting propertyand the semiconductor layer 102.

The other structures and effects thereof in FIG. 10A, FIG. 10B, and FIG.10C are the same as those in FIG. 2A, FIG. 3B, and FIG. 8B,respectively; therefore, the repeated explanation will be omitted. Referto the explanation of each corresponding drawing. Note that, althoughonly FIG. 2A in FIGS. 2A to 2C and only FIG. 3B in FIG. 3A to 3D aregiven as an example for explanation, it is possible to apply thestructures of FIGS. 10A to 10C to FIG. 2B, FIG. 3C, and FIG. 3D.

A semiconductor element according to the present invention each shown inFIGS. 11A to 11C includes a first electrode 100, an insulating film 101,a layer 106 e having an electron-transporting property, a secondelectrode 107, a third electrode 108, and a semiconductor layer 102 and,in the basic structure, FIGS. 11A, 11B, and 11C correspond to FIG. 6A,FIG. 7B, and FIG. 8D, respectively. The different portion in eachcorresponding structure is that the layer 106 e having anelectron-transporting property is formed to be in contact with each ofthe second electrode 107, the third electrode 108, and the semiconductorlayer 102.

In any of structures in FIGS. 11A to 11C, in the second electrode 107, alayer 103 or 103 a made of a second composite material is formed to bein contact at least with the layer 106 e having an electron-transportingproperty, and, in the third electrode 108, a layer 104 or 104 b made ofa first composite material is formed to be in contact at least with thesemiconductor layer 102.

In the semiconductor elements according to the present invention havingsuch a structure, electrons are injected into the layer 106 e having anelectron-transporting property from the second electrode 107 and holesare injected into the semiconductor layer 102 from the third electrode108 when voltage above a certain level is applied between the secondelectrode 107 and the third electrode 108 so that the voltage of thethird electrode 108 gets higher. Since injectability or transportabilityof holes and electrons can be improved by having such a structure, italso becomes possible to reduce a drive voltage. In addition, themolecules of the semiconductor layer 102 are excited as a result ofrecombining the injected electrons and holes, and light emission can beobtained upon the excited molecules returning to a ground state. In sucha structure, light emission can be obtained without applying a largeelectric field even when the electron-transporting property of thesemiconductor layer 102 is small.

As the material of the layer 106 e having an electron-transportingproperty, the following material having a comparatively highelectron-transporting property is used: a metal complex such astris(8-quinolinolato)aluminum (abbreviation: Alq₃);tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃);bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂);bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq); bis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp₂);bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂); orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)₂), anoxadiazole derivative such as2-(4-biphenylyl)-5-(4-tert-buthylphenyl)-1,3,4-oxadiazole (abbreviation:PBD) or 1,3-bis[5-(p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7), a triazole derivative such as3-(4-biphenylyl)-4-phenyl-5-(4-tert-buthylphenyl)-1,2,4-triazole(abbreviation: TAZ) or3-(4-biphenylyl)-4-(4-ethylpheyl)-5-(4-tert-buthylphenyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproin (abbreviation: BCP),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), 4,4-bis(5-methylbenzoxazol-2-yl)stilbene(abbreviation: BzOs), or the like. In the structures of FIGS. 11A to11C, the materials described in Embodiment Mode 1 can be used as thematerial of the semiconductor layer 102; however, the structures inFIGS. 11A to 11C are effective especially when the material having ahole-transporting property is used as a material generally said as ap-type semiconductor or a host material. Note that, in order torecombine holes and electrons easily, it is desirable to select as smallas possible the combination of an energy barrier of the layer 106 ehaving an electron-transporting property and the semiconductor layer102.

The other structures and effects thereof in FIGS. 11A, 11B, and 11C arethe same as those in FIG. 6A, FIG. 7B, and FIG. 8D, respectively;therefore, the repeated explanation will be omitted. Refer to theexplanation of each corresponding drawing. Note that, although only FIG.6A in FIGS. 6A to 6C and only FIG. 7B in FIG. 7A to 7D are given as anexample for explanation, it is possible to apply the structures of FIGS.11A to 11C to FIG. 6B, FIG. 7C, and FIG. 7D.

A semiconductor element according to the present invention each shown inFIGS. 12A to 12C includes a first electrode 100, an insulating film 101,a layer 106 h having a hole-transporting property, a second electrode107, a third electrode 108, and a semiconductor layer 102 and, in thebasic structure, FIGS. 12A, 12B, and 12C correspond to FIG. 6A, FIG. 7B,and FIG. 8D, respectively. The different portion in each correspondingstructure is that the layer 106 h having a hole-transporting property isformed to be in contact with each of the second electrode 107, the thirdelectrode 108, and the semiconductor layer 102.

In any of structures in FIGS. 12A to 12C, in the second electrode 107, alayer 103 or 103 a made of a second composite material is formed to bein contact at least with the semiconductor layer 102, and, in the thirdelectrode 108, a layer 104 or 104 b made of a first composite materialis formed to be in contact at least with the layer 106 h having ahole-transporting property.

In the semiconductor elements according to the present invention havingsuch a structure, electrons are injected into the semiconductor layer102 from the second electrode 107 and holes are injected into the layer106 h having a hole-transporting property from the third electrode 108when voltage above a certain level is applied between the secondelectrode 107 and the third electrode 108 so that the voltage of thethird electrode 108 gets higher. Since injectability or transportabilityof holes and electrons can be improved by having such a structure, italso becomes possible to reduce a drive voltage. In addition, themolecules of the semiconductor layer 102 are excited as a result ofrecombining the injected electrons and holes, and light emission can beobtained upon the excited molecules returning to a ground state. In sucha structure, light emission can be obtained without applying a largeelectric field even when the hole-transporting property of thesemiconductor layer 102 is small.

As the material of the layer 106 h having a hole-transporting property,the following material having a comparatively high hole-transportingproperty is used: 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB), 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl(abbreviation: TPD), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl(abbreviation: DNTPD), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), phthalocyanine (abbreviation: H₂ Pc), copperphthalocyanine (CuPc), vanadyl phthalocyanine (abbreviation: VOPc), orthe like. In the structures of FIGS. 12A to 12C, the materials describedin Embodiment Mode 1 can be used as the material of the semiconductorlayer 102; however, the structures in FIGS. 12A to 12C are effectiveespecially when the material having an electron-transporting property isused as a material generally said as a p-type semiconductor or a hostmaterial. Note that, in order to recombine holes and electrons easily,it is desirable to select as small as possible the combination of anenergy barrier of the layer 106 h having a hole-transporting propertyand the semiconductor layer 102.

The other structures and effects thereof in FIGS. 12A, 12B, and 12C arethe same as those in FIG. 6A, FIG. 7B, and FIG. 8D, respectively;therefore, the repeated explanation will be omitted. Refer to theexplanation of each corresponding drawing. Note that, although only FIG.6A in FIGS. 6A to 6C and only FIG. 7B in FIG. 7A to 7D are given as anexample for explanation, it is possible to apply the structures of FIGS.12A to 12C to FIG. 6B, FIG. 7C, and FIG. 7D.

Embodiment Mode 3

A method for manufacturing a semiconductor element according to thepresent invention will be explained with reference to FIGS. 13A to 13Eby giving FIG. 2C as an example.

First, a first electrode 15 made of tungsten is deposited over a quartzsubstrate 16 in 100 nm thick, an insulating film 12 made of silicondioxide (SiO₂) is deposited over the first electrode 15 in 100 nm thick,and conductive layers 17 a and 17 b made of tungsten are deposited overthe insulating film 12. After depositing tungsten over an entire surfaceof the substrate by a sputtering method or the like, a mask is formed byphotolithography, and the first electrode 15 is etched in a desiredshape. Either wet etching or dry etching may be used for the etching.The insulating film 12 is formed by a CVD method. In addition, theconductive layers 17 a and 17 b may be formed in the same manner as thefirst electrode 15. Moreover, over the conductive layer 17 a, a layer 13a made of a second composite material is deposited in 10 nm thick byco-evaporating Alq and lithium, using a mask, by vacuum vapor depositionusing resistance heating, such that a molar ratio between Alq andlithium is 1:0.01. Over the conductive layer 17 b, a layer 13 b made ofa first composite material is deposited in 10 nm thick by co-evaporatingmolybdenum oxide and NPB, using a mask, by vacuum vapor deposition usingresistance heating, such that a molar ratio between molybdenum oxide andNPB is 1:1. Accordingly, a second electrode including the conductivelayer 17 a and the layer 13 a made of the second composite material anda third electrode including the conductive layer 17 b and the layer 13 bmade of the first composite material are formed. Thereafter, pentaceneis deposited as a semiconductor layer 11 between the second electrodeand the third electrode by vapor deposition; thus, a semiconductorelement according to the present invention can be manufactured. Thesemiconductor layer 11 is preferably vapor-deposited with a mask.

A method for manufacturing a semiconductor element according to thepresent invention each illustrated in FIGS. 1A to 1C, FIGS. 2A and 2B,FIGS. 3A to 3D, FIGS. 5A to 5C, FIGS. 6A to 6C, FIGS. 7A to 7D, andFIGS. 8A to 8D basically does not have large difference except that theabove manufacturing order and the shape of the mask are changed. Notethat, in the case where a conductive layer is formed over thesemiconductor layer 11 as the structures illustrated in FIG. 1B and FIG.5B, the semiconductor layer 11 is less damaged if gold isvapor-deposited by vacuum vapor deposition using a mask.

Note that the semiconductor element according to the present inventioneach illustrated in FIGS. 9A to 9C, FIGS. 10A to 10C, FIGS. 11A to 11C,and FIGS. 12A to 12C can be manufactured by depositing the layer 106 hhaving a hole-transporting property or the layer 106 e having anelectron-transporting property in each predetermined position by a knownmethod such as a vacuum vapor deposition method. This can be performedappropriately by those skilled in the art. Although it is preferablethat a film thickness of the layer 106 h having a hole-transportingproperty or the layer 106 e having an electron-transporting property is10 to 100 nm, there is no limitation on the film thickness.

Embodiment Mode 4

In this embodiment mode, a light-emitting device according to thepresent invention using the semiconductor element described inEmbodiment mode 1 or 2 will be explained. Note that the light-emittingdevice according to the present invention includes in its category apanel where a pixel portion having a light-emitting element is formed, amodule where a means for controlling a semiconductor element such as anIC is mounted on the panel, and a module exteriorly provided with ameans for controlling a semiconductor element such as an IC.

FIGS. 14A and 14B show an example of a cross-sectional view (A) and atop view (B) of a light-emitting device according to the presentinvention, respectively. The light-emitting devices shown in FIGS. 14Aand 14B are each an extremely simple example of a light-emitting deviceaccording to the present invention, and a light-emitting deviceaccording to the present invention may have another structure other thanthis, of course. A light-emitting device according to the presentinvention is provided at least with a semiconductor element described inEmbodiment Mode 1 or 2 and a means for controlling the semiconductorelement.

In FIG. 14A, a base insulating film 201 is provided over a substrate200, and a first electrode 202 and an external connection portion 203are formed over the base insulating film 201. A first insulating film204 is formed to cover the first electrode 202, and a second electrodeincluding a layer 205 made of a second composite material and aconductive layer 207 a and a third electrode including a layer 206 madeof a first composite material and a conductive layer 207 b are providedthereover. Further, a semiconductor layer 208 is formed by covering thesecond electrode, the third electrode, and therebetween, and thus, asemiconductor element 214 is formed.

The semiconductor element 214 may be protected by a second insulatingfilm 209. A plurality of such semiconductor elements 214 is formed toform a display portion of a light-emitting device. A pixel portion wherethe semiconductor element 214 is formed is preferably protected from anexternal environment by being sealed by a sealing substrate 211 or thelike with the use of a sealant 210. Inert gas may be filled or a dryingagent may be provided in a space between the sealing substrate 211 andthe insulating film 209.

The external connection portion 203 is electrically connected to aflexible printed circuit (FPC) 213 or the like by interposing ananisotropic conductive film 212 therebetween. A signal from a means forcontrolling the semiconductor element 214 (not shown) is inputted intothe pixel portion through this FPC 213.

FIG. 14B is a schematic block diagram viewed from the top face of thelight-emitting device. In the light-emitting device in this embodimentmode, an element substrate 501 where the semiconductor element is formedis sealed with a sealing substrate 502, and a pixel portion 503 formedin the element substrate 501 is sealed by the sealing substrate 502 andthe sealant. A flexible printed circuit (FPC) is connected to anexternal connection portion 504 provided in a periphery of the pixelportion 503, and an external signal is inputted. Note that, as in thisembodiment mode, a driver circuit and the flexible printed circuit maybe provided independently or the both may be provided in combinationlike a TCP or the like where an IC chip is mounted on an FPC in which awiring pattern is formed.

Note that a mode of a sealing structure and module of a light-emittingdevice is not limited thereto, of course, and it is possible tomanufacture a light-emitting device by a known technique by following atechnique regarding an organic EL panel.

A light-emitting device according to the present invention can bemanufactured using a substrate that is extremely light like plastic buteasily affected by heat; therefore, an extremely lightweightlight-emitting device can be obtained. In addition, since plastic or thelike is flexible, a flexible light-emitting device can be obtained.Moreover, a light-emitting device according to the present invention hashigh yields because there is a few manufacturing elements and can bemanufactured inexpensively because of an advantage in reducing the cost.

Embodiment Mode 5

The light-emitting device shown in Embodiment Mode 4 can be mounted on atelephone handset, a television receiver, or the like as shown in FIGS.15A, 15B, and 15C. In addition, the light-emitting device may be mountedon a card having a function of managing personal information like an IDcard.

FIG. 15A shows a cellular phone handset according to the presentinvention, which includes a display portion 5551, an audio outputportion 5554, an audio input portion 5555, operation switches 5556 and5557, an antenna 5553, and the like in a main body 5552. Thelight-emitting device described in Embodiment Mode 4 is used for thedisplay portion 5551. The display portion 5551 of this cellular phonehandset is extremely light; therefore, a lightweight cellular phonehandset can be obtained. In addition, the display portion 5551 can bemanufactured inexpensively; therefore, a cellular phone handset superiorin cost performance can be obtained.

FIG. 15B is a television receiver according to the present invention,which includes a display portion 5531, a housing 5532, speakers 5533,and the like. The light-emitting device described in Embodiment Mode 4is used for the display portion 5531. The display portion 5531 of thistelevision receiver is extremely light; therefore, a lightweighttelevision receiver can be obtained. In addition, the display portion5531 can be manufactured inexpensively; therefore, a television receiversuperior in cost performance can be obtained.

FIG. 15C is an ID card according to the present invention, whichincludes a support body 5541, a display portion 5542, a integratedcircuit chip 5543 incorporated into the support body 5541, and the like.The light-emitting device described in Embodiment Mode 4 is used for thedisplay portion 5542. Note that integrated circuits 5544 and 5545 fordriving the display portion 5542 are also incorporated into the supportbody 5541. This ID card is kept in an extremely lightweight and thinshape while having the display portion 5542. In addition, the displayportion 5542 can be manufactured inexpensively; therefore, an ID cardthat can be manufactured inexpensively while having the display portion5542 can be obtained. Moreover, in the display portion 5542, it ispossible to display information that is inputted and outputted in theintegrated circuit chip 5543 and to confirm what kind of information isinputted and outputted, for example.

Embodiment Mode 6

As another embodiment mode according to the present invention, anexample where the semiconductor element described in Embodiment Mode 1or 2 is applied to a flexible light-emitting device will be shown withreference to FIG. 16.

A light-emitting device according to the present invention shown in FIG.16 may be placed in a housing, and a main body 610, a pixel portion 611for displaying an image, a driver IC 612, a receiver device 613, a filmbattery 614, and the like are included therein. The driver IC, thereceiver device, or the like may be mounted using a semiconductorcomponent. In a light-emitting device according to the presentinvention, a material for forming the main body 610 is formed of aflexible material such as plastic or a film. Although such a material iseasily affected by heat in many cases, it becomes possible tomanufacture a light-emitting device with a material that is easilyaffected by heat by forming a pixel portion with the use of thesemiconductor element described in Embodiment Mode 1 or 2.

Such a light-emitting device is extremely light and flexible; therefore,the light-emitting device can also be rolled up into a cylinder, whichis extremely advantageous in carrying. With the use of a light-emittingdevice according to the present invention, a display medium with alarge-sized screen can be carried freely.

In addition, such a light-emitting device according to the presentinvention has a high aperture ratio. Moreover, there is a fewmanufacturing elements compared with a light-emitting device using anorganic EL element; therefore, the light-emitting device has highyields. Further, the light-emitting device according to the presentinvention can be manufactured simply and easily. Furthermore, thelight-emitting device according to the present invention has a low drivevoltage and low power consumption.

Note that the light-emitting device shown in FIG. 16 can be used asmeans for mainly displaying a still image including an electrical homeappliance such as a refrigerator; a washing machine; a rice cooker; afixed telephone; a vacuum cleaner; and a clinical thermometer, arailroad wall banners, and a large-sized information display such as anarrival and departure guide plate in a railroad station and an airport,as well as a navigation system, an audio reproducing device (such as acar audio, an audio component, and the like), a personal computer, agame machine, and a portable information terminal (such as a mobilecomputer, a cellular phone, a portable game machine, an electronic book,and the like).

The present application is based on Japanese Patent Application serialNo. 2005-125807 filed on Apr. 22, 2005 in Japanese Patent Office, theentire contents of which are hereby incorporated by reference.

What is claimed is:
 1. A semiconductor element comprising: a firstelectrode; a semiconductor layer containing an organic material; aninsulating film which electrically insulates the first electrode and thesemiconductor layer; a second electrode which injects electrons into thesemiconductor layer; and a third electrode which injects holes into thesemiconductor layer, wherein the third electrode has at least partiallya layer comprising a first composite material wherein the firstcomposite material contains an organic material having ahole-transporting property and a metal oxide, wherein the secondelectrode has at least partially a layer comprising a second compositematerial wherein the second composite material contains an organicmaterial having an electron-transporting property and alkaline metal oralkaline earth metal, wherein the layer comprising the first compositematerial and the layer comprising the second composite material are eachin contact with the semiconductor layer, wherein the third electrode isformed of two layers of the layer comprising the first compositematerial and a conductive layer, and the conductive layer is in contactwith the semiconductor layer, wherein the second electrode is in contactwith the insulating film, and wherein the third electrode is in contactwith the insulating film.
 2. A semiconductor element according to claim1, wherein the conductive layer is formed between the semiconductorlayer and the layer comprising the first composite material.
 3. Asemiconductor element according to claim 1, wherein the semiconductorlayer emits light when voltage is applied between the second electrodeand the third electrode.
 4. A semiconductor element according to claim1, wherein the semiconductor layer emits light when voltage is appliedbetween the second electrode and the third electrode, and emissionluminance is changed by changing voltage applied to the first electrode.5. A semiconductor element according to claim 1, wherein the firstelectrode is a gate electrode, and the second electrode is a sourceelectrode, and the third electrode is a drain electrode.
 6. Asemiconductor element comprising: a first electrode; a semiconductorlayer containing an organic material; an insulating film whichelectrically insulates the first electrode and the semiconductor layer;a second electrode which injects electrons into the semiconductor layer;and a third electrode which injects holes into the semiconductor layer,wherein the third electrode has at least partially a layer comprising afirst composite material wherein the first composite material containsan organic material having a hole-transporting property and a metaloxide, wherein the second electrode has at least partially a layercomprising a second composite material wherein the second compositematerial contains an organic material having an electron-transportingproperty and alkaline metal or alkaline earth metal, wherein the layercomprising the first composite material and the layer comprising thesecond composite material are each in contact with the semiconductorlayer, wherein the second electrode is formed of two layers of the layercomprising the second composite material and a conductive layer, and theconductive layer is in contact with the semiconductor layer, wherein thesecond electrode is in contact with the insulating film, and wherein thethird electrode is in contact with the insulating film.
 7. Asemiconductor element according to claim 6, wherein the conductive layeris formed between the semiconductor layer and the layer comprising thesecond composite material.
 8. A semiconductor element according to claim6, wherein the semiconductor layer emits light when voltage is appliedbetween the second electrode and the third electrode.
 9. A semiconductorelement according to claim 6, wherein the semiconductor layer emitslight when voltage is applied between the second electrode and the thirdelectrode, and emission luminance is changed by changing voltage appliedto the first electrode.
 10. A semiconductor element according to claim6, wherein the first electrode is a gate electrode, and the secondelectrode is a source electrode, and the third electrode is a drainelectrode.
 11. A semiconductor element comprising: a first electrode; asemiconductor layer containing an organic material; an insulating filmbetween the first electrode and the semiconductor layer; a secondelectrode in contact with the insulating film; and a third electrode incontact with the insulating film, wherein the third electrode comprisesa conductive layer and a first layer comprising a first compositematerial, wherein the first composite material contains an organicmaterial having a hole-transporting property and a metal oxide, whereinthe second electrode comprises a second layer comprising a secondcomposite material, wherein the second composite material contains anorganic material having an electron-transporting property and alkalinemetal or alkaline earth metal, and wherein the first layer and thesecond layer are each in contact with the semiconductor layer.
 12. Asemiconductor element according to claim 11, wherein the conductivelayer is formed between the semiconductor layer and the first layer. 13.A semiconductor element according to claim 11, wherein the semiconductorlayer emits light when voltage is applied between the second electrodeand the third electrode.
 14. A semiconductor element according to claim11, wherein the semiconductor layer emits light when voltage is appliedbetween the second electrode and the third electrode, and emissionluminance is changed by changing voltage applied to the first electrode.15. A semiconductor element according to claim 11, wherein the firstelectrode is a gate electrode, and the second electrode is a sourceelectrode, and the third electrode is a drain electrode.
 16. Asemiconductor element comprising: a first electrode; a semiconductorlayer containing an organic material; an insulating film between thefirst electrode and the semiconductor layer; a second electrode incontact with the insulating film; and a third electrode in contact withthe insulating film, wherein the third electrode comprises a first layercomprising a first composite material, wherein the first compositematerial contains an organic material having a hole-transportingproperty and a metal oxide, wherein the second electrode comprises aconductive layer and a second layer comprising a second compositematerial, wherein the second composite material contains an organicmaterial having an electron-transporting property and alkaline metal oralkaline earth metal, and wherein the first layer and the second layerare each in contact with the semiconductor layer.
 17. A semiconductorelement according to claim 16, wherein the conductive layer is formedbetween the semiconductor layer and the second layer.
 18. Asemiconductor element according to claim 16, wherein the semiconductorlayer emits light when voltage is applied between the second electrodeand the third electrode.
 19. A semiconductor element according to claim16, wherein the semiconductor layer emits light when voltage is appliedbetween the second electrode and the third electrode, and emissionluminance is changed by changing voltage applied to the first electrode.20. A semiconductor element according to claim 16, wherein the firstelectrode is a gate electrode, and the second electrode is a sourceelectrode, and the third electrode is a drain electrode.